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<bits/stdc++.h>
using namespace std;
signed main(void){
	long long a=1,b;
	cin>>b;
	for(long long i=1;i<=b;i++)
		a*=i;
	cout<<a<<endl; 
}