import java.util.Scanner;

public class Main {
    public static void main(String[] args) {

        boolean isOk = false;

        Scanner sc = new Scanner(System.in);
        int target = Integer.parseInt(sc.next());
        int minDistance = sc.nextInt();
        int maxDistance = sc.nextInt();

        for (int i=minDistance;i <= maxDistance;i++){
            if (i%target == 0){
                isOk = true;
                break;
            }
        }
        if(isOk){
            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