import java.util.ArrayList;
import java.util.List;
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();
		List<Integer> X = new ArrayList<Integer>();
		List<Integer> Y = new ArrayList<Integer>();
		for(int i = 0; i*K <= B; i++) {
			if(i*K >= A) {
			X.add(i*K);
			}else {
			Y.add(i*K);
			}
		}
		if(X.size()==0) {
			System.out.println("NG");
		}else {
			System.out.println("OK");
		}
	}
}

/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