import java.io.*;
import java.util.*;
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 n=1;
    while(n<=(B/K))
    {
      if(A<=(K*n) && (K*n)<=B)
      {
        System.out.print("OK");
        return;
      }
      else
      n++;
    }
    System.out.print("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