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;for(std::cin>>n,i=n;i>1;n*=--i);std::cout<<n<<"\n";} 