import java.util.Scanner;

public class Main {

    public static void main(String[] args) {


        Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();
        if(A%K==0 || B%K==0){
            System.out.println("OK");
        }else{

        if((B-A)>=K){
            System.out.println("OK");
        }else{
            int p = A%K;
            if((K-p)<=(B-A)){
                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