diff --git a/.ocamlformat b/.ocamlformat
new file mode 100644
index 0000000..42476c9
--- /dev/null
+++ b/.ocamlformat
@@ -0,0 +1,2 @@
+profile = default
+version = 0.24.1
diff --git a/LICENCE b/LICENCE
new file mode 100644
index 0000000..954c185
--- /dev/null
+++ b/LICENCE
@@ -0,0 +1,12 @@
+Copyright (C) 2022 by vladan
+
+Permission to use, copy, modify, and/or distribute this software for any purpose
+with or without fee is hereby granted.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
+OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
+THIS SOFTWARE.
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..a10fc9f
--- /dev/null
+++ b/README.md
@@ -0,0 +1,13 @@
+# Advent of Code 2022 solutions in OCaml
+
+To run the a single day you'd need to run a nix development shell with:
+
+```
+$ nix develop
+```
+
+And then call the executable for e.g. day 1:
+
+```
+$ dune exec d1
+```
diff --git a/bin/d1/dune b/bin/d1/dune
new file mode 100644
index 0000000..39b707a
--- /dev/null
+++ b/bin/d1/dune
@@ -0,0 +1,4 @@
+(executable
+ (public_name d1)
+ (name main)
+ (libraries core utils))
diff --git a/bin/d1/input.txt b/bin/d1/input.txt
new file mode 100644
index 0000000..7d9f267
--- /dev/null
+++ b/bin/d1/input.txt
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diff --git a/bin/d1/main.ml b/bin/d1/main.ml
new file mode 100644
index 0000000..c16f304
--- /dev/null
+++ b/bin/d1/main.ml
@@ -0,0 +1,21 @@
+let sum_callories input =
+    let rec aux elv res = function
+        | [] -> elv :: res
+        | x :: xs -> if x = "" then aux 0 (elv :: res) xs
+                     else aux (elv + (int_of_string x)) res xs in
+    aux 0 [] input
+
+open Utils
+
+let summed = read_file "bin/d1/input.txt"
+            |> sum_callories
+            |> List.sort compare
+            |> List.rev ;;
+
+open Core
+
+let first = List.hd summed |> Option.value ~default:0 ;;
+let second = List.take summed 3 |> List.fold ~init:0 ~f:(+) ;;
+
+"\n1: " ^ (string_of_int first) ^
+"\n2: " ^ (string_of_int second) |> print_endline
diff --git a/bin/dune b/bin/dune
new file mode 100644
index 0000000..ab4a60a
--- /dev/null
+++ b/bin/dune
@@ -0,0 +1,3 @@
+(executable
+ (public_name aoc2022)
+ (name main))
diff --git a/bin/main.ml b/bin/main.ml
new file mode 100644
index 0000000..99e42f3
--- /dev/null
+++ b/bin/main.ml
@@ -0,0 +1,3 @@
+print_endline "\n" ;;
+print_endline "Nothing here. You can run an executable for a single day with:" ;;
+print_endline "dune exec d1" ;;
diff --git a/dune-project b/dune-project
new file mode 100644
index 0000000..6d33d2e
--- /dev/null
+++ b/dune-project
@@ -0,0 +1,23 @@
+(lang dune 3.2)
+
+(name aoc2022)
+
+(generate_opam_files false)
+
+(source
+ (uri https://gitea.vp.mk/vladan/aoc2022))
+
+(authors "Vladan Popovic")
+(maintainers "Vladan Popovic")
+
+(license LICENSE)
+
+(package
+ (name aoc2022)
+ (synopsis "Advent of Code 2022 solutions in OCaml")
+ (description "Advent of Code 2022 solutions in OCaml")
+ (depends ocaml dune)
+ (tags
+  (AoC2022 "Advent of Code")))
+
+; See the complete stanza docs at https://dune.readthedocs.io/en/stable/dune-files.html#dune-project
diff --git a/flake.lock b/flake.lock
new file mode 100644
index 0000000..549ba2e
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,57 @@
+{
+  "nodes": {
+    "flake-utils": {
+      "locked": {
+        "lastModified": 1667395993,
+        "narHash": "sha256-nuEHfE/LcWyuSWnS8t12N1wc105Qtau+/OdUAjtQ0rA=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "5aed5285a952e0b949eb3ba02c12fa4fcfef535f",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nix-filter": {
+      "locked": {
+        "lastModified": 1666547822,
+        "narHash": "sha256-razwnAybPHyoAyhkKCwXdxihIqJi1G6e1XP4FQOJTEs=",
+        "owner": "numtide",
+        "repo": "nix-filter",
+        "rev": "1a3b735e13e90a8d2fd5629f2f8363bd7ffbbec7",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "nix-filter",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1669867399,
+        "narHash": "sha256-Z8RXSFYOsIsTG96ROKtV0eZ8Q7u4irFWm6ELqfw7mT8=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "38e591dd05ffc8bdf79dc752ba78b05e370416fa",
+        "type": "github"
+      },
+      "original": {
+        "id": "nixpkgs",
+        "type": "indirect"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nix-filter": "nix-filter",
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 0000000..8399201
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,211 @@
+{
+  description = "A flake demonstrating how to build OCaml projects with Dune";
+
+  # Flake dependency specification
+  #
+  # To update all flake inputs:
+  #
+  #     $ nix flake update --commit-lockfile
+  #
+  # To update individual flake inputs:
+  #
+  #     $ nix flake lock --update-input <input> ... --commit-lockfile
+  #
+  inputs = {
+    # Convenience functions for writing flakes
+    flake-utils.url = "github:numtide/flake-utils";
+    # Precisely filter files copied to the nix store
+    nix-filter.url = "github:numtide/nix-filter";
+  };
+
+  outputs = { self, nixpkgs, flake-utils, nix-filter }:
+    # Construct an output set that supports a number of default systems
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        # Legacy packages that have not been converted to flakes
+        legacyPackages = nixpkgs.legacyPackages.${system};
+        # OCaml packages available on nixpkgs
+        ocamlPackages = legacyPackages.ocamlPackages;
+        # Library functions from nixpkgs
+        lib = legacyPackages.lib;
+
+        # Filtered sources (prevents unecessary rebuilds)
+        sources = {
+          ocaml = nix-filter.lib {
+            root = ./.;
+            include = [
+              ".ocamlformat"
+              "dune-project"
+              (nix-filter.lib.inDirectory "bin")
+              (nix-filter.lib.inDirectory "lib")
+              (nix-filter.lib.inDirectory "test")
+            ];
+          };
+
+          nix = nix-filter.lib {
+            root = ./.;
+            include = [
+              (nix-filter.lib.matchExt "nix")
+            ];
+          };
+        };
+      in
+      {
+        # Exposed packages that can be built or run with `nix build` or
+        # `nix run` respectively:
+        #
+        #     $ nix build .#<name>
+        #     $ nix run .#<name> -- <args?>
+        #
+        packages = {
+          # The package that will be built or run by default. For example:
+          #
+          #     $ nix build
+          #     $ nix run -- <args?>
+          #
+          default = self.packages.${system}.aoc2022;
+
+          aoc2022 = ocamlPackages.buildDunePackage {
+            pname = "aoc2022";
+            version = "0.1.0";
+            duneVersion = "3";
+            src = sources.ocaml;
+
+            strictDeps = true;
+
+            preBuild = ''
+              dune build aoc2022.opam
+            '';
+          };
+        };
+
+        # Flake checks
+        #
+        #     $ nix flake check
+        #
+        checks = {
+          # Run tests for the `aoc2022` package
+          aoc2022 =
+            let
+              # Patches calls to dune commands to produce log-friendly output
+              # when using `nix ... --print-build-log`. Ideally there would be
+              # support for one or more of the following:
+              #
+              # In Dune:
+              #
+              # - have workspace-specific dune configuration files
+              #
+              # In NixPkgs:
+              #
+              # - allow dune flags to be set in in `ocamlPackages.buildDunePackage`
+              # - alter `ocamlPackages.buildDunePackage` to use `--display=short`
+              # - alter `ocamlPackages.buildDunePackage` to allow `--config-file=FILE` to be set
+              patchDuneCommand =
+                let
+                  subcmds = [ "build" "test" "runtest" "install" ];
+                in
+                lib.replaceStrings
+                  (lib.lists.map (subcmd: "dune ${subcmd}") subcmds)
+                  (lib.lists.map (subcmd: "dune ${subcmd} --display=short") subcmds);
+            in
+
+            self.packages.${system}.aoc2022.overrideAttrs
+              (oldAttrs: {
+                name = "check-${oldAttrs.name}";
+                doCheck = true;
+                buildPhase = patchDuneCommand oldAttrs.buildPhase;
+                checkPhase = patchDuneCommand oldAttrs.checkPhase;
+                # skip installation (this will be tested in the `aoc2022-app` check)
+                installPhase = "touch $out";
+              });
+
+          # Check Dune and OCaml formatting
+          dune-fmt = legacyPackages.runCommand "check-dune-fmt"
+            {
+              nativeBuildInputs = [
+                ocamlPackages.dune_3
+                ocamlPackages.ocaml
+                legacyPackages.ocamlformat
+              ];
+            }
+            ''
+              echo "checking dune and ocaml formatting"
+              dune build \
+                --display=short \
+                --no-print-directory \
+                --root="${sources.ocaml}" \
+                --build-dir="$(pwd)/_build" \
+                @fmt
+              touch $out
+            '';
+
+          # Check documentation generation
+          dune-doc = legacyPackages.runCommand "check-dune-doc"
+            {
+              ODOC_WARN_ERROR = "true";
+              nativeBuildInputs = [
+                ocamlPackages.dune_3
+                ocamlPackages.ocaml
+                ocamlPackages.odoc
+              ];
+            }
+            ''
+              echo "checking ocaml documentation"
+              dune build \
+                --display=short \
+                --no-print-directory \
+                --root="${sources.ocaml}" \
+                --build-dir="$(pwd)/_build" \
+                @doc
+              touch $out
+            '';
+
+          # Check Nix formatting
+          nixpkgs-fmt = legacyPackages.runCommand "check-nixpkgs-fmt"
+            { nativeBuildInputs = [ legacyPackages.nixpkgs-fmt ]; }
+            ''
+              echo "checking nix formatting"
+              nixpkgs-fmt --check ${sources.nix}
+              touch $out
+            '';
+        };
+
+        # Development shells
+        #
+        #    $ nix develop .#<name>
+        #    $ nix develop .#<name> --command dune build @test
+        #
+        # [Direnv](https://direnv.net/) is recommended for automatically loading
+        # development environments in your shell. For example:
+        #
+        #    $ echo "use flake" > .envrc && direnv allow
+        #    $ dune build @test
+        #
+        devShells = {
+          default = legacyPackages.mkShell {
+            # Development tools
+            packages = [
+              # Source file formatting
+              legacyPackages.nixpkgs-fmt
+              legacyPackages.ocamlformat
+              # For `dune build --watch ...`
+              legacyPackages.fswatch
+              # For `dune build @doc`
+              ocamlPackages.odoc
+              # OCaml editor support
+              ocamlPackages.ocaml-lsp
+              # Nicely formatted types on hover
+              ocamlPackages.ocamlformat-rpc-lib
+              # Fancy REPL thing
+              ocamlPackages.utop
+              ocamlPackages.core
+            ];
+
+            # Tools from packages
+            inputsFrom = [
+              self.packages.${system}.aoc2022
+            ];
+          };
+        };
+      });
+}
diff --git a/lib/dune b/lib/dune
new file mode 100644
index 0000000..8d1d8a6
--- /dev/null
+++ b/lib/dune
@@ -0,0 +1,2 @@
+(library
+ (name utils))
diff --git a/lib/utils.ml b/lib/utils.ml
new file mode 100644
index 0000000..0f1ada6
--- /dev/null
+++ b/lib/utils.ml
@@ -0,0 +1,11 @@
+let read_file name =
+    let ic = open_in name in
+    let try_read () =
+        try Some (input_line ic)
+        with End_of_file -> None in
+    let rec aux acc =
+        match try_read () with
+        | Some s -> aux (s::acc)
+        | None -> close_in ic; acc in
+    aux []
+
diff --git a/test/aoc2022.ml b/test/aoc2022.ml
new file mode 100644
index 0000000..e69de29
diff --git a/test/dune b/test/dune
new file mode 100644
index 0000000..42a4677
--- /dev/null
+++ b/test/dune
@@ -0,0 +1,2 @@
+(test
+ (name aoc2022))