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 int x=1,s;
cin>>s;
while(s!=1){
x*=s;
s--;
}
cout<<x<<endl;
return 0;
}