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();
      
      int B1 =(B/K)*K;
      
      if(A<=B1){
        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