#include <iostream>

// Write a program to find the greatest common
// divisor of two non-negative integers with the
// following requirements:
//
//     gcd( 0, 0 ) = 0
//     gcd( 0, n ) = n
//     gcd( m, 0 ) = m
//
// Otherwise, the gcd is the largest positive
// integer that divides both integers.
//
// If either integer is negative, return 0.
//
// Note that the only tool you have right now is
// a for loop, so this is not the most efficient
// way to solve this problem. Later, we will see
// a much more efficient algorithm.

// Function declarations
int main();

// Function definitions
int main() {
    return 0;
}





























// Hint: An integer 'k' divides an integer 'm'
// if m%k == 0.
//
// If both integers are positive, how large
// could their greatest common divisor possibly
// be?






























// Here is one solution, but scroll down for
// a better solution.
/*
int main() {
    int m{};
    std::cout << "Enter a non-negative integer: ";
    std::cin  >> m;

    int n{};
    std::cout << "Enter another non-negative integer: ";
    std::cin  >> n;

    if ( (m < 0) || (n < 0) ) {
        return 0;
    }

    if ( m == 0 ) {
        std::cout << "gcd(" << m << ", " << n << ") = "
                  << n << std::endl;
        return 0;
    }

    if ( n == 0 ) {
        std::cout << "gcd(" << m << ", " << n << ") = "
                  << m << std::endl;
        return 0;
    }

    int smaller{ m };

    if ( n < smaller ) {
        smaller = n;
    }

    int gcd{ 1 };

    for ( int k{ 2 }; k <= smaller; ++k ) {
        if ( (m%k == 0) && (n%k == 0) ) {
            gcd = k;
        }
    }

    std::cout << "gcd(" << m << ", " << n << ") = "
              << gcd << std::endl;

    return 0;
}
*/





































// Here is a better solution. Why is it better?
/*
int main() {
    int m{};
    std::cout << "Enter a non-negative integer: ";
    std::cin  >> m;

    int n{};
    std::cout << "Enter another non-negative integer: ";
    std::cin  >> n;

    if ( (m < 0) || (n < 0) ) {
        return 0;
    }

    if ( m == 0 ) {
        std::cout << "gcd(" << m << ", " << n << ") = "
                  << n << std::endl;
        return 0;
    }

    if ( n == 0 ) {
        std::cout << "gcd(" << m << ", " << n << ") = "
                  << m << std::endl;
        return 0;
    }

    int smaller{ m };

    if ( n < smaller ) {
        smaller = n;
    }

    for ( int k{ smaller }; k >= 1; --k ) {
        if ( (m%k == 0) && (n%k == 0) ) {
            std::cout << "gcd(" << m << ", " << n << ") = "
                      << k << std::endl;

            // We started with the largest possible
            // divisor and worked downward, so the
            // first common divisor must be the gcd.
            return 0;
        }
    }

    // We should never reach this statement because
    // 1 divides every positive integer.
    std::cout << "We should never get here..."
              << std::endl;

    return 0;
}
*/