#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(n);++i)
#define all(a) (a).begin(),(a).end()
#define dunk(a) cout << (a) << endl
using namespace std;
typedef long long ll;

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	string a, b;
	cin >> a >> b;

	vector<char> num = { '1','2','3','4','5','6','7','8','9','0' };
	int judge1 = 0;
	int judge2 = 0;
	rep(i, 10) {
		judge1 += count(all(a), num[i]);
		judge2 += count(all(b), num[i]);
	}
	if (judge1 != a.size() || judge2 != b.size()) {
		puts("NG");
		return 0;
	}

	if (a.substr(0, 2) == "00" || b.substr(0, 2) == "00") {
		puts("NG");
		return 0;
	}

	puts("OK");
	return 0;
}