#include <iostream>
#include <vector>
#include <set>
#include <queue>
#include <algorithm>
#include <string>
#include <cmath>
#include <functional>
#include <iomanip>
#include <map>

#define _USE_MATH_DEFINES
#include <math.h>
using namespace std;
#define MAX 100000
char ic[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };
int main() {
	string a, b;
	bool f = true;
	bool zero = true;
	cin >> a >> b;
	for (int i = 0; i < a.length(); ++i) {
		if (find(ic, ic + 10, a[i]) == end(ic)) {
			f = false;
			break;
		}
		else {
			if (zero) {
				if (i != a.length() - 1 && a[i] == '0') {
					f = false;
					break;

				}
				else {
					zero = false;
				}
			}
		}
	}
	for (int i = 0; i < b.length() && f; ++i) {
		if (find(ic, ic + 10, b[i]) == end(ic)) {
			f = false;
			break;
		}
		else {
			if (zero) {
				if (i != b.length() - 1 && b[i] == '0') {
					f = false;
					break;

				}
				else {
					zero = false;
				}
			}
		}
	}
	cout << (f ? "OK" : "NG") << endl;
	return 0;
}