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 n=5, sum = 1;
   cin >> n;
   for(long i = 1;i <= n;++i){
      sum *= i;
  }
  cout << sum << endl;
 return 0;
}