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>
#include <algorithm>
using namespace std;
int main(){
int n;
cin >>n;
int b;
b=1;
long long int c;
c=1;
while(b<=n){
c=c*b;
b=b+1;}
cout <<c<<endl;}