#include <bits/stdc++.h>
using namespace std;

bool solve() {
    string A, B;
    cin >> A >> B;
    for (char x : A) if (!isdigit(x)) return false;
    for (char x : B) if (!isdigit(x)) return false;
    if (A != "0" && A[0] == '0') return false;
    if (B != "0" && B[0] == '0') return false;
    return true;
}

int main() {
    puts(solve() ? "OK" : "NG");
}