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;
  long long a = 1;
  scanf("%d", &n);
  for (int i = 2; i <= n; ++i) {
    a *= i;
  }
  printf("%lld\n", a);
}
