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

int main() {
    int K, a, b;
    string ret = "NG";

    cin >> K >> a >> b;

    for(int i = a; i <= b; i++) {
        if(i % K == 0) {
            ret = "OK";
            break;
        }
    }

    cout << ret << endl;
    return 0;
}