#include <iostream>
#include <cmath>
using namespace std;

long long n;

long long fac(long long n)
{
    if(n == 0)     return 1;
    if(n == 1)     return 1;

    return n * fac( n - 1 );
}


int main()
{

        cin >> n;
        if(n >= 0) cout << fac(n);
}