import java.util.Scanner;

public class Main{
    public static void main(final String args[]) {
        Scanner scan = new Scanner(System.in);
        int K = scan.nextInt();
        int A = scan.nextInt();
        int B = scan.nextInt();
        int Kc = K;
        while(true){
            if(Kc <= B){
                if(Kc >= A){
                    System.out.println("OK");
                    break;
                }
            }else if(Kc > B){
                System.out.println("NG");
                break;
            }
            Kc = Kc + K;
            
        }

    }
}
/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