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 res = 1;
  for (auto i=1; i<=N; i++) {
    res *= i;
  }
  cout << res << endl;
}