#include <bits/stdc++.h>

using namespace std;

int main(){
    int k, a, b;
    cin >> k >> a >> b;
    bool sol = false;
    for(int i = a; i <= b; i++){
        if(i % k == 0)
            sol = true;
    }
    cout << (sol ? "OK": "NG") << '\n';
}