#include<iostream>
#include<iomanip>
#include<algorithm>
#include<math.h>
#include<vector>
using namespace std;

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

	if (k == 1) {
		cout << "OK";
	}
	else {
		if((b - a) /k > 0)
			cout << "OK";
		else
			cout << "NG";
	}
	return 0;
}