Problem:
Factorial

Write a program which reads an integer n and prints the factorial of n. You can assume that n ≤ 20.

Input

An integer n (1 ≤ n ≤ 20) in a line.

Output

Print the factorial of n in a line.

Sample Input

5

Output for the Sample Input

120

Solution in Scala (judge verdict: Accepted)

object Main extends App {
  def fact(n: Long): Long = n match {
    case 1 => 1
    case n => n * fact(n-1)
  }
  val n = readInt()
  println(fact(n))
}