import java.util.*;

class Main {
    final Scanner sc = new Scanner(System.in);

    public static void main(String[] args) {
        new Main().run();
    }

    private void run() {
        int n = sc.nextInt();
        Set<Long> set = new HashSet<>();
        for (int i = 0; i < n; i++) {
            long a = sc.nextInt();
            if (set.contains(a)) {
                System.out.println("NO");
                return;
            }
            set.add(a);
        }
        System.out.println("YES");
    }
} import java.util.*; util.* java class Main {
    final Scanner sc = new Scanner(System.in);

    public static void main(String[] args) {
        new Main().run();
    }

    private void run() {
        int n = sc.nextInt();
        Set<Long> set = new HashSet<>();
        for (int i = 0; i < n; i++) {
            long a = sc.nextInt();
            if (set.contains(a)) {
                System.out.println("NO");
                return;
            }
            set.add(a);
        }
        System.out.println("YES");
    }
} Main final Scanner sc = new Scanner(System.in); sc new Scanner(System.in) public static void main(String[] args) {
        new Main().run();
    } main {
        new Main().run();
    } new Main().run() new Main().run new Main() String[] args args private void run() {
        int n = sc.nextInt();
        Set<Long> set = new HashSet<>();
        for (int i = 0; i < n; i++) {
            long a = sc.nextInt();
            if (set.contains(a)) {
                System.out.println("NO");
                return;
            }
            set.add(a);
        }
        System.out.println("YES");
    } run {
        int n = sc.nextInt();
        Set<Long> set = new HashSet<>();
        for (int i = 0; i < n; i++) {
            long a = sc.nextInt();
            if (set.contains(a)) {
                System.out.println("NO");
                return;
            }
            set.add(a);
        }
        System.out.println("YES");
    } int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc Set<Long> set = new HashSet<>(); set new HashSet<>() for (int i = 0; i < n; i++) {
            long a = sc.nextInt();
            if (set.contains(a)) {
                System.out.println("NO");
                return;
            }
            set.add(a);
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
            long a = sc.nextInt();
            if (set.contains(a)) {
                System.out.println("NO");
                return;
            }
            set.add(a);
        } {
            long a = sc.nextInt();
            if (set.contains(a)) {
                System.out.println("NO");
                return;
            }
            set.add(a);
        } long a = sc.nextInt(); a sc.nextInt() sc.nextInt sc if (set.contains(a)) {
                System.out.println("NO");
                return;
            } set.contains(a) set.contains set a {
                System.out.println("NO");
                return;
            } System.out.println("NO") System.out.println System.out System System.out "NO" return; set.add(a) set.add set a System.out.println("YES") System.out.println System.out System System.out "YES"
import java.util.*;

class Main {
    final Scanner sc = new Scanner(System.in);

    public static void main(String[] args) {
        new Main().run();
    }

    private void run() {
        int n = sc.nextInt();
        Set<Long> set = new HashSet<>();
        for (int i = 0; i < n; i++) {
            long a = sc.nextInt();
            if (set.contains(a)) {
                System.out.println("NO");
                return;
            }
            set.add(a);
        }
        System.out.println("YES");
    }
}
