import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;

public class Main {

    private static Scanner sc;
    private static int N;

    public static void main(String[] args) {

        sc = new Scanner(System.in);
        N = sc.nextInt();

        System.out.println(solve() ? "YES" : "NO");

    }

    private static boolean solve() {
        Set<Long> set = new HashSet<>();

        for (int i = 0; i < N; i++) {
            if (!set.add(sc.nextLong())) {
                return false;
            }
        }
        return true;
    }

} import java.util.HashSet; HashSet java.util import java.util.Scanner; Scanner java.util import java.util.Set; Set java.util public class Main {

    private static Scanner sc;
    private static int N;

    public static void main(String[] args) {

        sc = new Scanner(System.in);
        N = sc.nextInt();

        System.out.println(solve() ? "YES" : "NO");

    }

    private static boolean solve() {
        Set<Long> set = new HashSet<>();

        for (int i = 0; i < N; i++) {
            if (!set.add(sc.nextLong())) {
                return false;
            }
        }
        return true;
    }

} Main private static Scanner sc; sc private static int N; N public static void main(String[] args) {

        sc = new Scanner(System.in);
        N = sc.nextInt();

        System.out.println(solve() ? "YES" : "NO");

    } main {

        sc = new Scanner(System.in);
        N = sc.nextInt();

        System.out.println(solve() ? "YES" : "NO");

    } sc = new Scanner(System.in) sc new Scanner(System.in) N = sc.nextInt() N sc.nextInt() sc.nextInt sc System.out.println(solve() ? "YES" : "NO") System.out.println System.out System System.out solve() ? "YES" : "NO" solve() solve "YES" "NO" String[] args args private static boolean solve() {
        Set<Long> set = new HashSet<>();

        for (int i = 0; i < N; i++) {
            if (!set.add(sc.nextLong())) {
                return false;
            }
        }
        return true;
    } solve {
        Set<Long> set = new HashSet<>();

        for (int i = 0; i < N; i++) {
            if (!set.add(sc.nextLong())) {
                return false;
            }
        }
        return true;
    } Set<Long> set = new HashSet<>(); set new HashSet<>() for (int i = 0; i < N; i++) {
            if (!set.add(sc.nextLong())) {
                return false;
            }
        } int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
            if (!set.add(sc.nextLong())) {
                return false;
            }
        } {
            if (!set.add(sc.nextLong())) {
                return false;
            }
        } if (!set.add(sc.nextLong())) {
                return false;
            } !set.add(sc.nextLong()) set.add(sc.nextLong()) set.add set sc.nextLong() sc.nextLong sc {
                return false;
            } return false; false return true; true public class Main {

    private static Scanner sc;
    private static int N;

    public static void main(String[] args) {

        sc = new Scanner(System.in);
        N = sc.nextInt();

        System.out.println(solve() ? "YES" : "NO");

    }

    private static boolean solve() {
        Set<Long> set = new HashSet<>();

        for (int i = 0; i < N; i++) {
            if (!set.add(sc.nextLong())) {
                return false;
            }
        }
        return true;
    }

} public class Main {

    private static Scanner sc;
    private static int N;

    public static void main(String[] args) {

        sc = new Scanner(System.in);
        N = sc.nextInt();

        System.out.println(solve() ? "YES" : "NO");

    }

    private static boolean solve() {
        Set<Long> set = new HashSet<>();

        for (int i = 0; i < N; i++) {
            if (!set.add(sc.nextLong())) {
                return false;
            }
        }
        return true;
    }

} Main
import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;

public class Main {

    private static Scanner sc;
    private static int N;

    public static void main(String[] args) {

        sc = new Scanner(System.in);
        N = sc.nextInt();

        System.out.println(solve() ? "YES" : "NO");

    }

    private static boolean solve() {
        Set<Long> set = new HashSet<>();

        for (int i = 0; i < N; i++) {
            if (!set.add(sc.nextLong())) {
                return false;
            }
        }
        return true;
    }

}
