import java.util.*;
public class Main{
  
 public static void main(String[] args){
  
   Scanner sc = new Scanner(System.in);
   
     /*K倍*/
     int k = sc.nextInt();
     int a = sc.nextInt();
     int b= sc.nextInt();
   
   int seisu;
   int count = 0;
   for(int i=a;i<=b;i++){
     
     if(i%k == 0){ 
       seisu = i/k;
      
         count++;    
         break;
       
     }
   }
     
   if(count>0){
     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