import java.util.Arrays;
import java.util.HashSet;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) throws Exception {
        final Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        final HashSet<Integer> integers = new HashSet<>();
        for (int i = 0; i < n; i++) {
            integers.add(sc.nextInt());
        }
        System.out.println(integers.size() == n ? "YES" : "NO");
    }
} import java.util.Arrays; Arrays java.util import java.util.HashSet; HashSet java.util import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) throws Exception {
        final Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        final HashSet<Integer> integers = new HashSet<>();
        for (int i = 0; i < n; i++) {
            integers.add(sc.nextInt());
        }
        System.out.println(integers.size() == n ? "YES" : "NO");
    }
} Main public static void main(String[] args) throws Exception {
        final Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        final HashSet<Integer> integers = new HashSet<>();
        for (int i = 0; i < n; i++) {
            integers.add(sc.nextInt());
        }
        System.out.println(integers.size() == n ? "YES" : "NO");
    } main {
        final Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        final HashSet<Integer> integers = new HashSet<>();
        for (int i = 0; i < n; i++) {
            integers.add(sc.nextInt());
        }
        System.out.println(integers.size() == n ? "YES" : "NO");
    } final Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc final HashSet<Integer> integers = new HashSet<>(); integers new HashSet<>() for (int i = 0; i < n; i++) {
            integers.add(sc.nextInt());
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
            integers.add(sc.nextInt());
        } {
            integers.add(sc.nextInt());
        } integers.add(sc.nextInt()) integers.add integers sc.nextInt() sc.nextInt sc System.out.println(integers.size() == n ? "YES" : "NO") System.out.println System.out System System.out integers.size() == n ? "YES" : "NO" integers.size() == n integers.size() integers.size integers n "YES" "NO" String[] args args public class Main {
    public static void main(String[] args) throws Exception {
        final Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        final HashSet<Integer> integers = new HashSet<>();
        for (int i = 0; i < n; i++) {
            integers.add(sc.nextInt());
        }
        System.out.println(integers.size() == n ? "YES" : "NO");
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        final Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        final HashSet<Integer> integers = new HashSet<>();
        for (int i = 0; i < n; i++) {
            integers.add(sc.nextInt());
        }
        System.out.println(integers.size() == n ? "YES" : "NO");
    }
} Main
import java.util.Arrays;
import java.util.HashSet;
import java.util.Scanner;

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