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