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<limits>
using namespace std;
int main(){
	int n;
	long long s = 1;
	cin >>n;
	for(int i=1; i<=n; i++){s*=i;}
	cout <<s<<endl;
}