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();
      String ans = "NG";
      int ak = A / K;
      for(int i = ak; i * K <= B; i++){
        int ik = i * K;
        if(A <= ik && ik <= B){
          ans = "OK";
          break;
        }
      }
      System.out.println(ans);
    } 
}
/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