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

int main()
{
    string a,b;
    cin >> a >> b;

    bool flag = true;
    if((a.length() != 1 && a[0] == '0') || (b.length() != 1 && b[0] == '0')) flag = false;
    for(int i = 0; i < a.length(); i++){
        if(!(a[i] >= '0' && a[i] <= '9')) flag = false;
    }
    for(int i = 0; i < b.length(); i++){
        if(!(b[i] >= '0' && b[i] <= '9')) flag = false;
    }

    cout << (flag ? "OK" : "NG") << endl;

    return 0;
}