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diff --git a/2024/OCaml/lib/day_02/part_01.ml b/2024/OCaml/lib/day_02/part_01.ml
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+++ b/2024/OCaml/lib/day_02/part_01.ml
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+(* Day 2: Part 1 *)
+
+type level = int
+type reports = level list list
+
+let rec compare_report_levels_helper comparison prev report =
+  match report with
+  | [] -> true
+  | h :: t -> comparison prev h && compare_report_levels_helper comparison h t
+
+let compare_report_levels comparison report =
+  match report with
+  | [] -> true
+  | h :: t -> compare_report_levels_helper comparison h t
+
+let all_increasing report = compare_report_levels ( < ) report
+let all_decreasing report = compare_report_levels ( > ) report
+
+let at_least_one report =
+  compare_report_levels (fun prev curr -> prev <> curr) report
+
+let at_most_three report =
+  compare_report_levels (fun prev curr -> abs (prev - curr) <= 3) report
+
+let check_report_safety report =
+  if not (all_increasing report || all_decreasing report) then false
+  else if not (at_least_one report && at_most_three report) then false
+  else true
+
+let rec count_safe_reports acc lst =
+  match lst with
+  | [] -> acc
+  | h :: t ->
+      if h then count_safe_reports (acc + 1) t else count_safe_reports acc t
+
+let solve reports =
+  reports |> List.map check_report_safety |> count_safe_reports 0
+
+let line_to_report line =
+  line |> String.split_on_char ' ' |> List.map int_of_string
+
+let lines_to_reports lines = List.map line_to_report lines