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 ans = 1;
for(long long i=1; i<=n; i++) ans *= i;
cout<<ans<<endl;
}