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 x;
	unsigned long long int ret=1;
	cin >> x;
	for(int i=1;i<=x;i++)
		ret*=i;
	if(!x)ret=0;
	cout << ret << endl;
}