#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair <int,int> PAIR;
const int N = 1e4+5;
const int M = 1e4;
const int INF = 0x3f3f3f3f;

int main() {
	int n,a,b;
	scanf("%d",&n); 
	scanf("%d%d",&a,&b);
	
	for(int i = a;i <= b;++i){
		if(i % n == 0){
			printf("OK\n");
			return 0;
		}
	}
	printf("NG\n");
    return 0;
}