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

int k, a, b;

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