fun readLargeInt () =
    valOf (TextIO.scanStream (LargeInt.scan StringCvt.DEC) TextIO.stdIn)


fun findAns 1 w = w
  | findAns d w = 
    findAns (d - 1) (w - (w div (d * d)))


val () =
    let
        val w = readLargeInt ()
        val d = readLargeInt ()

        val ans = findAns d w
    in
        print (LargeInt.toString ans)
    end