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

long long int k, a, b;

void solve() {
	cin >> k >> a >> b;
	int flag = 0;
	for (int i = a; i <= b; i++) {
		if (i % k == 0) {
			flag = 1;
			break;
		}
	}
	if (flag)
		cout << "OK";
	else
		cout << "NG";
}

int main()
{
#ifndef ONLINE_JUDGE
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);
#endif

	ios_base::sync_with_stdio(false);
	cin.tie(NULL);

	solve();

	return 0;
}