#include <bits/stdc++.h>

//const static double	de_PI	= 3.14159265358979323846;
//const static double	de_EPS	= 0.000001;
//const static int	de_MOD = 1000000007;
//const static int	de_MAX = 999999999;
//const static int	de_MIN = -999999999;

int main(void) {

	//std::ifstream inf("123.txt");	std::cin.rdbuf(inf.rdbuf());

	std::string A, B;
	std::cin >> A >> B;

	for (unsigned int i = 0; i < A.length(); i++) {
		if (A[i] < '0' || '9' < A[i]) {
			std::cout << "NG" << std::endl;
			return 0;
		}
	}
	for (unsigned int i = 0; i < A.length(); i++) {
		if (B[i] < '0' || '9' < B[i]) {
			std::cout << "NG" << std::endl;
			return 0;
		}
	}

	int a = std::stoi(A);
	if (a > 12345) {
		std::cout << "NG" << std::endl;
		return 0;
	}

	int b = std::stoi(B);
	if (b > 12345) {
		std::cout << "NG" << std::endl;
		return 0;
	}

	if (A != std::to_string(a)) {
		std::cout << "NG" << std::endl;
		return 0;
	}

	if (B != std::to_string(b)) {
		std::cout << "NG" << std::endl;
		return 0;
	}

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

}