import java.util.*;
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 x = ( a/k + 1 ) * k;
            
      if (x <= b || a % k == 0 || b % k == 0 || k == 1) {
         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