let string_of_list to_s list = 
  "[" ^ String.concat ", " (List.map to_s list) ^ "]"
let string_of_ints = string_of_list string_of_int
let string_of_intss = string_of_list string_of_ints
let reshape n list = 
  let rec aux yss ys m = function
    | [] -> yss
    | x :: xs when n = m -> aux ((x :: ys) :: yss) [] 1 xs
    | x :: xs -> aux yss (x :: ys) (m + 1) xs
  in aux [] [] 1 (List.rev list)
let () = print_endline (string_of_intss (reshape 2 [1;2;3;4]))

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