import java.util.Scanner;
 
public class Main{
 
	public static void main(String[] args) {
 
		Scanner scanner = new Scanner(System.in);
 
		int K = scanner.nextInt();
		int A = scanner.nextInt();
		int B = scanner.nextInt();
 
		int total = (B / K) * K;
		
		if (A <= total) {
			System.out.println("OK");
		} else {
			System.out.println("NG");
		}
		scanner.close();
     
	}
}
/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