#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <cctype>

int main() {
    std::string a, b;

    std::cin >> a >> b;

    if ((a.length() > 1 && a[0] == '0') || (b.length() > 1 && b[0] == '0')) {
        std::cout << "NG" << std::endl;
        return 0;
    }

    for (int i = 0; i < a.length(); i++) {
        if (!isdigit(a[i])) {
            std::cout << "NG" << std::endl;
            return 0;
        }
    }

    for (int i = 0; i < b.length(); i++) {
        if (!isdigit(b[i])) {
            std::cout << "NG" << std::endl;
            return 0;
        }
    }

    std::cout << "OK" << std::endl;

    return 0;
}