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()
{
 int x;
 long long int sum=1;
 while(cin>>x)
 {
 for(int i=1; i<=x; i++)
 {
 sum*=i;
 }
 cout<<sum<<endl;
}
return 0;
}