#include <vector>
#include <list>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <algorithm>
#include <sstream>
#include <iostream>
#include <string>
#include <cstdio>
#include <cmath>

using namespace std;

int main() {

	string A, B;
	cin >> A >> B;
	bool flag = true, t;

	t = true;
	for (int i = 0; i < A.size(); i++) {
		if ((A[i]=='0' && t && A.size() != 1) || ('9' < A[i] || A[i] < '0')) flag = false;
		if ('1' <= A[i] && A[i] <= '9') t = false;
	}

	t = true;
	for (int i = 0; i < B.size(); i++) {
		if ((B[i] == '0' && t && A.size() != 1) || ('9' < B[i] || B[i] < '0')) flag = false;
		if ('1' <= B[i] && B[i] <= '9') t = false;
	}

	if (flag) cout << "OK" << endl;
	else cout << "NG" << endl;

	return 0;
}