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() {
  long long n, r = 1;
  cin >> n;
  for (; n > 1; n--)
    r *= n;
  cout << r << endl;
  return 0;
}