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 a[21],b;
	a[0]=1;
	for(int i=1;i<=20;i++)a[i]=a[i-1]*i;
	cin>>b;
	cout<<a[b]<<endl;
	return 0;
} 
