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;
	long long r=1;
	cin>>n;
	
	for(int i=n;i>=1;i--){
		r*=i;
	}
	cout<<r<<endl;
		
	return 0;
}      