let coin_change coins target =
  let dp = Array.make (target + 1) (target + 1) in
  dp.(0) <- 0;
  for i = 1 to target do
    List.iter (fun c ->
      if c <= i && dp.(i - c) + 1 < dp.(i) then
        dp.(i) <- dp.(i - c) + 1
    ) coins
  done;
  if dp.(target) > target then -1
  else dp.(target)

;;

coin_change [1; 5; 10; 25] 67