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.

Example

Input

5


Output

120
#include <stdio.h>

long long f(int n) {
  return n == 1 ? 1 : n * f(n - 1);
}

int main(void) {
  int n;
  scanf("%d", &n);
  printf("%lld\n", f(n));
  return 0;
}
