// helloworld.cpp

#include <iostream>

int faculty(int n ){
    if(n > 0)
        return n * faculty(n-1);
    else
        return 1;
}

int main(){
    int n, f;
    std::cout << "Calculate faculty of: ";

    std::cin >> n;

    f = faculty(n);

    std::cout << f;

    return 0;
}