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(void)
{
	int n;
	cin>>n;
	long long int ans=1;
	for(int i=1;i<=n;i++)
	{
		ans*=i;
	}
	cout<<ans<<endl;
	cin>>n;
}