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 <iostream>
using namespace std;
int main() {
  int n;
  cin >> n;
  long long f = 1;
  for (int i = 1; i <= n; i++)
    f *= i;
  cout << f << endl;
}