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

bool ok( string a, string b ){
  for( int i = 0; i < a.size(); ++i )
    if( not ( '0' <= a[ i ] and a[ i ] <= '9' ) )
      return false;
  for( int i = 0; i < b.size(); ++i )
    if( not ( '0' <= b[ i ] and b[ i ] <= '9' ) )
      return false;
  return true;
}

signed main(){
  string A, B; cin >> A >> B;
  if( not ok( A, B ) )
    cout << "NG" << endl;
  else
    cout << "OK" << endl;
  return 0;
}