#include <iostream>
#include <string>
#include <map>
#include <vector>
#include <bitset>
#include <iomanip>
#include <deque>

using namespace std;

int main()
{
    int a, b, k;
    cin >> k;
    cin >> a >> b;

    for (int i = a; i <= b; i++) {
        if (i % k == 0) {
            cout << "OK" << endl;
            return (0);
        }
    }

    cout << "NG" << endl;

}
