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>
int main(){long long n,i;std::cin>>n;for(i=n;--n;)i*=n;std::cout<<i<<"\n";}