import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
import java.util.*;

public class Main {
  public static void main(String[] args) throws IOException {
    BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    int K = Integer.parseInt(in.readLine());
    StringTokenizer st = new StringTokenizer(in.readLine());
    int A = Integer.parseInt(st.nextToken());
    int B = Integer.parseInt(st.nextToken());
    for(int score=A; score<=B; score++){
      if(score%K==0){
        System.out.println("OK");
        break;
      } else if(score==B && score%K!=0){
        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