#include "iostream"
using namespace std;

char letter[2][6];
int start[2];
int num[2];

int main() {
	cin >> letter[1] >> letter[0];
	for (int i = 0; letter[0][i] != NULL;i++) {
		if ((letter[0][i] >= 'a'&&letter[0][i] <= 'z') || (letter[0][i] >= 'A'&&letter[0][i] <= 'Z')) {
			cout << "NG\n";
			return 0;
		}
	}
	for (int i = 0; letter[1][i] != NULL; i++) {
		if ((letter[1][i] >= 'a'&&letter[1][i] <= 'z') || (letter[1][i] >= 'A'&&letter[1][i] <= 'Z')) {
			cout << "NG\n";
			return 0;
		}
	}
	start[0] = letter[0][0] - '0';
	start[1] = letter[1][0] - '0';
	if (start[0] == 0 && letter[0][1] != NULL) {
		cout << "NG\n";
		return 0;
	}
	if (start[1] == 0 && letter[1][1] != NULL) {
		cout << "NG\n";
		return 0;
	}
	for (int i = 0; letter[0][i] != NULL; i++) {
		num[0] *= 10;
		num[0] += letter[0][i]-'0';
	}
	if (num[0] > 12345) {
		cout << "NG\n";
		return 0;
	}
	for (int i = 0; letter[1][i] != NULL; i++) {
		num[1] *= 10;
		num[1] += letter[1][i]-'0';
	}
	if (num[1] > 12345) {
		cout << "NG\n";
		return 0;
	}
	cout << "OK\n";
	return 0;
}