#include <algorithm>
#include <cassert>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <map>
#include <memory>
#include <numeric>
#include <set>
#include <stack>
#include <string>
#include <vector>

#define rep(i,a,b) for(int i=(a);i<(b);++i)
#define MOD 1000000007
#define int long long
using ll = long long;
using namespace std;
const int INF = 1LL << 50;
using P = pair<int, int>;

template <class T>
bool chmin(T &a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    else {
        return false;
    }
}
template <class T>
bool chmax(T &a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    else {
        return false;
    }
}
struct Setup {
    Setup() {
        cin.tie(0);
        ios::sync_with_stdio(false);
        cout << fixed << setprecision(20);
    }
} SETUP;

bool check(string s) {
    if (s.size() != 1 && s[0] == '0') {
        return false;
    }
    if (s.size() >= 5 && s > "12345") {
        return false;
    }
    for (auto c : s) {
        if ('a' <= c && c <= 'z') {
            return false;
        }
        else if ('A' <= c&&c <= 'Z') {
            return false;
        }
    }
    return true;
}

signed main() {
    string a, b; cin >> a >> b;
    string ans = (check(a) && check(b)) ? "OK" : "NG";
    cout << ans << endl;
}