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

public class Repetition2 {


	private String isRepeated(String file) throws FileNotFoundException {

		HashSet<String> words = new HashSet<String>();
		String[] wordsArray = file.split(" ");

		if (wordsArray.length != 0) {
			for (String word : wordsArray) {
				if (!words.contains(word)) {
					words.add(word);
				} else
					return "no";
			}
			return "yes";
		}

		return "File empty";

	}

	public static void main(String[] args) throws FileNotFoundException {

		Scanner sc = new Scanner(System.in);

		Repetition2 r = new Repetition2();

		String answer = r.isRepeated("/Users/mariasamo/oop/ALDA/src/test2.txt");
//		String answer = r.isRepeated(sc.nextLine());

		System.out.println(answer);

	}

}