import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        HashSet<Integer> c = new HashSet<Integer>();
        for (int i = 0; i < n; i++) {
                c.add(sc.nextInt());
        }
        if(c.size() == n)
        System.out.println("YES");
        else
        System.out.println("NO");
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        HashSet<Integer> c = new HashSet<Integer>();
        for (int i = 0; i < n; i++) {
                c.add(sc.nextInt());
        }
        if(c.size() == n)
        System.out.println("YES");
        else
        System.out.println("NO");
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        HashSet<Integer> c = new HashSet<Integer>();
        for (int i = 0; i < n; i++) {
                c.add(sc.nextInt());
        }
        if(c.size() == n)
        System.out.println("YES");
        else
        System.out.println("NO");
    } main {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        HashSet<Integer> c = new HashSet<Integer>();
        for (int i = 0; i < n; i++) {
                c.add(sc.nextInt());
        }
        if(c.size() == n)
        System.out.println("YES");
        else
        System.out.println("NO");
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc HashSet<Integer> c = new HashSet<Integer>(); c new HashSet<Integer>() for (int i = 0; i < n; i++) {
                c.add(sc.nextInt());
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                c.add(sc.nextInt());
        } {
                c.add(sc.nextInt());
        } c.add(sc.nextInt()) c.add c sc.nextInt() sc.nextInt sc if(c.size() == n)
        System.out.println("YES");
        else
        System.out.println("NO"); c.size() == n c.size() c.size c n System.out.println("YES") System.out.println System.out System System.out "YES" System.out.println("NO") System.out.println System.out System System.out "NO" String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        HashSet<Integer> c = new HashSet<Integer>();
        for (int i = 0; i < n; i++) {
                c.add(sc.nextInt());
        }
        if(c.size() == n)
        System.out.println("YES");
        else
        System.out.println("NO");
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        HashSet<Integer> c = new HashSet<Integer>();
        for (int i = 0; i < n; i++) {
                c.add(sc.nextInt());
        }
        if(c.size() == n)
        System.out.println("YES");
        else
        System.out.println("NO");
    }
} Main
import java.util.*;

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