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;
long long fact(int n){
  if(n==2) return 2;
  return fact(n-1)*n;
}
 
int main(void){
  int n;
  cin >> n;
  cout << fact(n) << endl;
}