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

#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<endl
#define p2(s, t) cout << (s) << " " << (t) << endl
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << endl
#define p_yes() p("Yes")
#define p_no() p("No")

bool check(string s){
    // all number?
    for(char c : s){
        if(!isdigit(c)){
            return false;
        }
    }

    // leading zero
    if(s.size()>1 && s[0]=='0') return false;
    
    return true;
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    // input
    string s, t;
    cin >> s >> t;

    if(check(s) && check(t)){
        p("OK");
    }else{
        p("NG");
    }
    
    return 0;
}