import java.util.Scanner;

class Main{
  public static void main(String[]args){
    Scanner  sc=new Scanner(System.in);
    int k,a,b;
    k=sc.nextInt();
    a=sc.nextInt();
    b=sc.nextInt();
    boolean flag=true	;
    for(int i=a;i<=b;i++){
      if(i%k==0){
        System.out.println("OK");
       flag=false;
        break;
      }
    }
    if(flag)
      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