import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Integer quantity = sc.nextInt();
        Set<Integer> NumSet = new HashSet<Integer>();
        boolean flg = false;
        for (int i = 0; i < quantity; i++){
            if (!NumSet.add(sc.nextInt())) {
                flg = true;
                System.out.println("NO");
                break;
            }
        }
        if (!flg) {
            System.out.println("YES");
        }
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Integer quantity = sc.nextInt();
        Set<Integer> NumSet = new HashSet<Integer>();
        boolean flg = false;
        for (int i = 0; i < quantity; i++){
            if (!NumSet.add(sc.nextInt())) {
                flg = true;
                System.out.println("NO");
                break;
            }
        }
        if (!flg) {
            System.out.println("YES");
        }
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Integer quantity = sc.nextInt();
        Set<Integer> NumSet = new HashSet<Integer>();
        boolean flg = false;
        for (int i = 0; i < quantity; i++){
            if (!NumSet.add(sc.nextInt())) {
                flg = true;
                System.out.println("NO");
                break;
            }
        }
        if (!flg) {
            System.out.println("YES");
        }
    } main {
        Scanner sc = new Scanner(System.in);
        Integer quantity = sc.nextInt();
        Set<Integer> NumSet = new HashSet<Integer>();
        boolean flg = false;
        for (int i = 0; i < quantity; i++){
            if (!NumSet.add(sc.nextInt())) {
                flg = true;
                System.out.println("NO");
                break;
            }
        }
        if (!flg) {
            System.out.println("YES");
        }
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) Integer quantity = sc.nextInt(); quantity sc.nextInt() sc.nextInt sc Set<Integer> NumSet = new HashSet<Integer>(); NumSet new HashSet<Integer>() boolean flg = false; flg false for (int i = 0; i < quantity; i++){
            if (!NumSet.add(sc.nextInt())) {
                flg = true;
                System.out.println("NO");
                break;
            }
        } int i = 0; int i = 0; i 0 i < quantity i quantity i++ i++ i {
            if (!NumSet.add(sc.nextInt())) {
                flg = true;
                System.out.println("NO");
                break;
            }
        } {
            if (!NumSet.add(sc.nextInt())) {
                flg = true;
                System.out.println("NO");
                break;
            }
        } if (!NumSet.add(sc.nextInt())) {
                flg = true;
                System.out.println("NO");
                break;
            } !NumSet.add(sc.nextInt()) NumSet.add(sc.nextInt()) NumSet.add NumSet sc.nextInt() sc.nextInt sc {
                flg = true;
                System.out.println("NO");
                break;
            } flg = true flg true System.out.println("NO") System.out.println System.out System System.out "NO" break; if (!flg) {
            System.out.println("YES");
        } !flg flg {
            System.out.println("YES");
        } System.out.println("YES") System.out.println System.out System System.out "YES" String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Integer quantity = sc.nextInt();
        Set<Integer> NumSet = new HashSet<Integer>();
        boolean flg = false;
        for (int i = 0; i < quantity; i++){
            if (!NumSet.add(sc.nextInt())) {
                flg = true;
                System.out.println("NO");
                break;
            }
        }
        if (!flg) {
            System.out.println("YES");
        }
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Integer quantity = sc.nextInt();
        Set<Integer> NumSet = new HashSet<Integer>();
        boolean flg = false;
        for (int i = 0; i < quantity; i++){
            if (!NumSet.add(sc.nextInt())) {
                flg = true;
                System.out.println("NO");
                break;
            }
        }
        if (!flg) {
            System.out.println("YES");
        }
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Integer quantity = sc.nextInt();
        Set<Integer> NumSet = new HashSet<Integer>();
        boolean flg = false;
        for (int i = 0; i < quantity; i++){
            if (!NumSet.add(sc.nextInt())) {
                flg = true;
                System.out.println("NO");
                break;
            }
        }
        if (!flg) {
            System.out.println("YES");
        }
    }
}