#include <iostream>

using namespace std;

int main()
{
    ios_base::sync_with_stdio(0);
    int k, a, b;
    cin >> k >> a >> b;
    for (int i = a; i <= b; ++i)
    {
        if (i % k == 0)
        {
            cout << "OK";
            return 0;
        }
    }
    cout << "NG";
    return 0;
}
