import java.util.Scanner;
//int[] date=new int[2];
public class Main {
int i,o,sum,h,s,e,u,ty,yu,ui,n,num,qw;
double m,t,r,j,k,f,d,g,w;
static double l;
String b,c,z,x,v,a,q;
Scanner scan =new Scanner(System.in);
//入力
	public void input() {	
	
	}
	//演算
	public void compute() {
	
		}
//出力
	public void output() {
h=scan.nextInt();
int[] date=new int[2];
for(o=0;o<2;o++) {
	date[o]=scan.nextInt();
}
while(true) {
	e+=1;
	o=h*e;
	if(o>=date[0]&&o<=date[1]) {
		System.out.println("OK");
		break;
	}else if(o<date[0]){
		
	}else {
		System.out.println("NG");
		break;
	}

}
		}
	public static void main(String [ ] args) {
		Main p = new  Main ();
		p.input();
		p.compute();
		p.output();
		}
	}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz