
import java.util.*;
public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

        Set s = new HashSet<Integer>();

        int n = sc.nextInt();

        boolean out = false;
        for (int i = 0; i < n; i++) {
            int a = sc.nextInt();
            Integer e = new Integer(a);
            if (s.contains(e)) {
                System.out.println("NO");
                out = true;
                break;
            } else {
                s.add(e);
            }
        }

        if (!out) {
            System.out.println("YES");
        }
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

        Set s = new HashSet<Integer>();

        int n = sc.nextInt();

        boolean out = false;
        for (int i = 0; i < n; i++) {
            int a = sc.nextInt();
            Integer e = new Integer(a);
            if (s.contains(e)) {
                System.out.println("NO");
                out = true;
                break;
            } else {
                s.add(e);
            }
        }

        if (!out) {
            System.out.println("YES");
        }
    }
} Main public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

        Set s = new HashSet<Integer>();

        int n = sc.nextInt();

        boolean out = false;
        for (int i = 0; i < n; i++) {
            int a = sc.nextInt();
            Integer e = new Integer(a);
            if (s.contains(e)) {
                System.out.println("NO");
                out = true;
                break;
            } else {
                s.add(e);
            }
        }

        if (!out) {
            System.out.println("YES");
        }
    } main {
        Scanner sc = new Scanner(System.in);

        Set s = new HashSet<Integer>();

        int n = sc.nextInt();

        boolean out = false;
        for (int i = 0; i < n; i++) {
            int a = sc.nextInt();
            Integer e = new Integer(a);
            if (s.contains(e)) {
                System.out.println("NO");
                out = true;
                break;
            } else {
                s.add(e);
            }
        }

        if (!out) {
            System.out.println("YES");
        }
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) Set s = new HashSet<Integer>(); s new HashSet<Integer>() int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc boolean out = false; out false for (int i = 0; i < n; i++) {
            int a = sc.nextInt();
            Integer e = new Integer(a);
            if (s.contains(e)) {
                System.out.println("NO");
                out = true;
                break;
            } else {
                s.add(e);
            }
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
            int a = sc.nextInt();
            Integer e = new Integer(a);
            if (s.contains(e)) {
                System.out.println("NO");
                out = true;
                break;
            } else {
                s.add(e);
            }
        } {
            int a = sc.nextInt();
            Integer e = new Integer(a);
            if (s.contains(e)) {
                System.out.println("NO");
                out = true;
                break;
            } else {
                s.add(e);
            }
        } int a = sc.nextInt(); a sc.nextInt() sc.nextInt sc Integer e = new Integer(a); e new Integer(a) if (s.contains(e)) {
                System.out.println("NO");
                out = true;
                break;
            } else {
                s.add(e);
            } s.contains(e) s.contains s e {
                System.out.println("NO");
                out = true;
                break;
            } System.out.println("NO") System.out.println System.out System System.out "NO" out = true out true break; {
                s.add(e);
            } s.add(e) s.add s e if (!out) {
            System.out.println("YES");
        } !out out {
            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);

        Set s = new HashSet<Integer>();

        int n = sc.nextInt();

        boolean out = false;
        for (int i = 0; i < n; i++) {
            int a = sc.nextInt();
            Integer e = new Integer(a);
            if (s.contains(e)) {
                System.out.println("NO");
                out = true;
                break;
            } else {
                s.add(e);
            }
        }

        if (!out) {
            System.out.println("YES");
        }
    }
} public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

        Set s = new HashSet<Integer>();

        int n = sc.nextInt();

        boolean out = false;
        for (int i = 0; i < n; i++) {
            int a = sc.nextInt();
            Integer e = new Integer(a);
            if (s.contains(e)) {
                System.out.println("NO");
                out = true;
                break;
            } else {
                s.add(e);
            }
        }

        if (!out) {
            System.out.println("YES");
        }
    }
} Main

import java.util.*;
public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

        Set s = new HashSet<Integer>();

        int n = sc.nextInt();

        boolean out = false;
        for (int i = 0; i < n; i++) {
            int a = sc.nextInt();
            Integer e = new Integer(a);
            if (s.contains(e)) {
                System.out.println("NO");
                out = true;
                break;
            } else {
                s.add(e);
            }
        }

        if (!out) {
            System.out.println("YES");
        }
    }
}