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

#define ll long long
#define pb push_back
#define iter std::vector<int>::iterator

int main() {
	ios_base ::sync_with_stdio(0);
	cin.tie(0);

	int d, a, b;

	cin >> d >> a >> b;

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

	cout << "NG";
	

	return 0;
}