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

public class Main {

    public static void main(String[] args) {
        @SuppressWarnings("resource")
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Set<Integer> set = new HashSet<>();
        for (int i = 0 ; i < n ; i++) {
            set.add(sc.nextInt());
        }
        System.out.println(set.size() == n ? "YES" : "NO");
    }

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

    public static void main(String[] args) {
        @SuppressWarnings("resource")
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Set<Integer> set = new HashSet<>();
        for (int i = 0 ; i < n ; i++) {
            set.add(sc.nextInt());
        }
        System.out.println(set.size() == n ? "YES" : "NO");
    }

} Main public static void main(String[] args) {
        @SuppressWarnings("resource")
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Set<Integer> set = new HashSet<>();
        for (int i = 0 ; i < n ; i++) {
            set.add(sc.nextInt());
        }
        System.out.println(set.size() == n ? "YES" : "NO");
    } main {
        @SuppressWarnings("resource")
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Set<Integer> set = new HashSet<>();
        for (int i = 0 ; i < n ; i++) {
            set.add(sc.nextInt());
        }
        System.out.println(set.size() == n ? "YES" : "NO");
    } @SuppressWarnings("resource")
        Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc Set<Integer> set = new HashSet<>(); set new HashSet<>() for (int i = 0 ; i < n ; i++) {
            set.add(sc.nextInt());
        } int i = 0 ; int i = 0 ; i 0 i < n i n i++ i++ i {
            set.add(sc.nextInt());
        } {
            set.add(sc.nextInt());
        } set.add(sc.nextInt()) set.add set sc.nextInt() sc.nextInt sc System.out.println(set.size() == n ? "YES" : "NO") System.out.println System.out System System.out set.size() == n ? "YES" : "NO" set.size() == n set.size() set.size set n "YES" "NO" String[] args args public class Main {

    public static void main(String[] args) {
        @SuppressWarnings("resource")
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Set<Integer> set = new HashSet<>();
        for (int i = 0 ; i < n ; i++) {
            set.add(sc.nextInt());
        }
        System.out.println(set.size() == n ? "YES" : "NO");
    }

} public class Main {

    public static void main(String[] args) {
        @SuppressWarnings("resource")
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Set<Integer> set = new HashSet<>();
        for (int i = 0 ; i < n ; i++) {
            set.add(sc.nextInt());
        }
        System.out.println(set.size() == n ? "YES" : "NO");
    }

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

public class Main {

    public static void main(String[] args) {
        @SuppressWarnings("resource")
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Set<Integer> set = new HashSet<>();
        for (int i = 0 ; i < n ; i++) {
            set.add(sc.nextInt());
        }
        System.out.println(set.size() == n ? "YES" : "NO");
    }

}
