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();
      boolean H=false;
      while(B>=A){
         if(B%K==0){
            H=true;
         }
         B--;
      }
      if(H==true){
         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