import java.util.Set;
import java.io.*;
import java.util.*;
import java.io.BufferedOutputStream;
import java.io.PrintWriter;
import java.util.HashSet;

public class Main {
    public static void main(final String[] args) {
        final FastScanner scanner = new FastScanner();
        try (final FastWriter writer = new FastWriter()) {
            int N = scanner.nextInt();
            Set<Long> s = new HashSet<>();
            for (int i = 0; i < N; i++) {
                long j = scanner.nextLong();
                if (s.contains(j)) {
                    writer.println("NO");
                    return;
                }
                s.add(j);
            }
            writer.println("YES");
        }
    }
}

class FastScanner {
    private final BufferedReader br;
    private StringTokenizer st;

    public FastScanner() {
        br = new BufferedReader(new InputStreamReader(System.in));
    }

    public String next() {
        while (st == null || !st.hasMoreElements()) {
            try {
                st = new StringTokenizer(br.readLine());
            } catch (final IOException e) {
                e.printStackTrace();
            }
        }
        return st.nextToken();
    }

    public int nextInt() {
        return Integer.parseInt(next());
    }

    public long nextLong() {
        return Long.parseLong(next());
    }

    public double nextDouble() {
        return Double.parseDouble(next());
    }

    public String nextLine() {
        String str = "";
        try {
            str = br.readLine();
        } catch (final IOException e) {
            e.printStackTrace();
        }
        return str;
    }
}

class FastWriter extends PrintWriter {
    public FastWriter() {
        super(new BufferedOutputStream(System.out));
    }

    public static void main(final String[] args) {
        try (final FastWriter w = new FastWriter()) {
            w.println(32);
        }
    }
}


/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