#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using Graph = vector<vector<int>>;
int main() {
  string S; cin >> S;
  string T; cin >> T;
  string alpha = "0123456789";
  int a = 0;
  int b = 0;
  int za = 0;
  int zb = 0;
  for(int i = 0;i < S.size(); i++) {
    bool fire = false;
    for(int j = 0; j < alpha.size(); j++) {
      if(alpha[j] == S[i]) {
        fire = true;
      }
    }
    if(fire) {
      a++;
    }
    if('0' == S[0] && i != S.size() - 1) {
      za++;
    }
  }
  for(int i = 0;i < T.size(); i++) {
    bool fire = false;
    for(int j = 0; j < alpha.size(); j++) {
      if(alpha[j] == T[i]) {
        fire = true;
      }
    }
    if(fire) {
      b++;
    }
    if('0' == T[0] && i != T.size() - 1) {
      zb++;
    }
  }

  if(a == S.size() && b == T.size() && za == 0 && zb == 0 && stoi(S) <= 12345 && stoi(T) <= 12345) {
    cout << "OK" << endl;
  }else {
    cout << "NG" << endl;
  }
}