import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		int K = stdIn.nextInt();
		int A = stdIn.nextInt();
		int B = stdIn.nextInt();
		
		int ans = K;
		
		for(int i = 1; ; i++) {
			if(A <= ans) {
				break;
			}else {
				ans += K;
			}
		}
		
		if(ans <= B) {
			System.out.println("OK");
		}else {
			System.out.println("NG");
		}
	}

}
/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