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