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 n,i,sum=1;
	cin>>n;
	for(i=1;i<=n;i++){
		sum=sum*i;
	}
	cout<<sum<<endl;
	return 0;
}