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

int main(){
    int K, A, B;
    cin >> K;
    cin >> A >> B;

    for(int i=A; i<=B; i++){
        if(i%K==0){
            cout << "OK" << endl;
            return 0;
        }
    }
    cout << "NG" << endl;

    return 0;
}