#include <bits/stdc++.h>
using namespace std;
int parse(string x){
    
    int res = 0;
    for(int i = 0; i < x.size(); ++i){
        if('0' > x[i] or '9' < x[i]) return -1;
        res *= 10;
        res += x[i]-'0';
    }
    
    if(res > 12345) return -1;
    if(x[0] == '0' and res > 0) return -1;
    
    return res;
}

int main(){

    string a, b;
    cin >> a >> b;
    int A = parse(a), B = parse(b);
    if(A < 0 or B < 0) 
        cout << "NG" << '\n';
    else
        cout << "OK" << '\n';
    
    return 0;
}