#include <iostream>
#include <cstdlib>
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";
            return 0;
        }
    }
    cout << "NG";
}