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

int to_i(string s){
  stringstream ss;
  int res;
  ss << s; 
  ss >> res;
  return res;
}

string to_s(int n){
  stringstream ss;
  string res;
  ss << n;
  ss >> res;
  return res;
}

bool check(string s){
  for(int i = 0;i < (int)s.size();++i){
    if(s[i] - '0' < 0 ||
       s[i] - '0' > 9)return false;
  }
  int n = to_i(s);
  if(n < 0 || n > 12345)return false;
  return s == to_s(n);
}

int main(void){
  string a,b;
  cin >> a >> b;
  if(check(a) && check(b))puts("OK");
  else puts("NG");
  return 0;
}