import java.util.*;

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();
        for(int i = a; i <= b; i++){
            if(i % k == 0) {
                System.out.println("OK");
                return;
            }
        }
        System.out.println("NG");
        scan.close();
    }
}
/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