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 int ans = 1;
int n;
cin >> n;
for(int i=1; i<=n; i++)
ans*=i;
cout << ans << endl;

return 0;
}