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 <cstdio>

using namespace std;

int main() {
  int n;
  scanf("%d", &n);

  unsigned long p = 1;
  for (; n > 1; p *= n--) {}

  printf("%ld\n", p);
  return 0;
}