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 int i,s=1,n;
    cin>>n;
    for(i=n;i>0;i--) s=s*i;
    cout<<s<<endl;


    return 0;
}