import java.util.Scanner;
public class Main
{
  public static void main(String[] args)
  {
    Scanner sc = new Scanner(System.in);
    int x = sc.nextInt();
    int y  = sc.nextInt();
    int z  = sc.nextInt(); 
    boolean b = true;
    for(int i = y; i <= z; i++)
    {
      if(i % x == 0)
        b = false;
    }
    if(b == false)
      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