import java.io.*;
import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);
//        DecimalFormat df = new DecimalFormat("0.00000000");
        
        final int N = Integer.parseInt(sc.next());
        Set<String> set = new HashSet<>();
        for (int i = 0; i < N; i++) {
            set.add(sc.next());
        }
        out.println(set.size() == N ? "YES" : "NO");
        
        out.flush();
    }
} import java.io.*; io.* java import java.util.*; util.* java public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);
//        DecimalFormat df = new DecimalFormat("0.00000000");
        
        final int N = Integer.parseInt(sc.next());
        Set<String> set = new HashSet<>();
        for (int i = 0; i < N; i++) {
            set.add(sc.next());
        }
        out.println(set.size() == N ? "YES" : "NO");
        
        out.flush();
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);
//        DecimalFormat df = new DecimalFormat("0.00000000");
        
        final int N = Integer.parseInt(sc.next());
        Set<String> set = new HashSet<>();
        for (int i = 0; i < N; i++) {
            set.add(sc.next());
        }
        out.println(set.size() == N ? "YES" : "NO");
        
        out.flush();
    } main {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);
//        DecimalFormat df = new DecimalFormat("0.00000000");
        
        final int N = Integer.parseInt(sc.next());
        Set<String> set = new HashSet<>();
        for (int i = 0; i < N; i++) {
            set.add(sc.next());
        }
        out.println(set.size() == N ? "YES" : "NO");
        
        out.flush();
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) PrintWriter out = new PrintWriter(System.out); out new PrintWriter(System.out) final int N = Integer.parseInt(sc.next()); N Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc Set<String> set = new HashSet<>(); set new HashSet<>() for (int i = 0; i < N; i++) {
            set.add(sc.next());
        } int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
            set.add(sc.next());
        } {
            set.add(sc.next());
        } set.add(sc.next()) set.add set sc.next() sc.next sc out.println(set.size() == N ? "YES" : "NO") out.println out set.size() == N ? "YES" : "NO" set.size() == N set.size() set.size set N "YES" "NO" out.flush() out.flush out String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);
//        DecimalFormat df = new DecimalFormat("0.00000000");
        
        final int N = Integer.parseInt(sc.next());
        Set<String> set = new HashSet<>();
        for (int i = 0; i < N; i++) {
            set.add(sc.next());
        }
        out.println(set.size() == N ? "YES" : "NO");
        
        out.flush();
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);
//        DecimalFormat df = new DecimalFormat("0.00000000");
        
        final int N = Integer.parseInt(sc.next());
        Set<String> set = new HashSet<>();
        for (int i = 0; i < N; i++) {
            set.add(sc.next());
        }
        out.println(set.size() == N ? "YES" : "NO");
        
        out.flush();
    }
} Main
import java.io.*;
import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);
//        DecimalFormat df = new DecimalFormat("0.00000000");
        
        final int N = Integer.parseInt(sc.next());
        Set<String> set = new HashSet<>();
        for (int i = 0; i < N; i++) {
            set.add(sc.next());
        }
        out.println(set.size() == N ? "YES" : "NO");
        
        out.flush();
    }
}