import java.util.*;
import java.io.*;

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();

    if (a % k == 0 || b % k == 0){
      System.out.println("OK");
      return;
    }

      int rem = a % k;
      int temp = a-rem;
      temp += k;
      for(int i=temp; i<b; i+=k){
        if(temp > a){
          System.out.println("OK");
          return;
        }
      }
      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