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(void)
{
unsigned int n;
cin>>n;
unsigned long long int ans=n;
while(n>1){
    ans*=--n;
}
cout<<ans<<endl;

return 0;
}