import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		int k = sc.nextInt();
		int a = sc.nextInt();
		int b = sc.nextInt();
		int s =k;
		
		while(true) {
			if(a<=k && k <= b) {
				System.out.println("OK");
				break;
			}else if(b<k) {
				System.out.println("NG");
				break;
			}
			k+=s;
		}
	}
	
}
/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