import java.util.Scanner;
public class Main {

    public static void main(String[] args) {
        Scanner scan=new Scanner(System.in);
int K= scan.nextInt();

        int A= scan.nextInt();

        int B= scan.nextInt();

        int N=A%K;
        if((N+B-A>=K)||(N==0)){System.out.println("OK");}
        else {System.out.println("NG");};



        // write your code here
    }
}
/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