AtCoder Beginner Contest 055: B - Training Camp

LargeIntとIntInfの違いとは。

implementation

fun fact(n) =
  let
    fun go(0, acc) = acc
    |   go(n, acc) = go(n-1, n * acc mod 1000000007)
  in
    Int.fromLarge(go(Int.toLarge(n), 1))
  end

fun readInt() = TextIO.scanStream (Int.scan StringCvt.DEC) TextIO.stdIn
val SOME n = readInt()
val () = print(Int.toString(fact(n)) ^ "\n")