import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        HashMap<Integer,Integer> A = new HashMap<>();
        for (int i = 0; i < N; i++){
            int a = sc.nextInt();
            if (A.containsKey(a)){
                System.out.println("NO");
                return;
            }
            A.put(a,0);
        }
        System.out.println("YES");
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        HashMap<Integer,Integer> A = new HashMap<>();
        for (int i = 0; i < N; i++){
            int a = sc.nextInt();
            if (A.containsKey(a)){
                System.out.println("NO");
                return;
            }
            A.put(a,0);
        }
        System.out.println("YES");
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        HashMap<Integer,Integer> A = new HashMap<>();
        for (int i = 0; i < N; i++){
            int a = sc.nextInt();
            if (A.containsKey(a)){
                System.out.println("NO");
                return;
            }
            A.put(a,0);
        }
        System.out.println("YES");
    } main {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        HashMap<Integer,Integer> A = new HashMap<>();
        for (int i = 0; i < N; i++){
            int a = sc.nextInt();
            if (A.containsKey(a)){
                System.out.println("NO");
                return;
            }
            A.put(a,0);
        }
        System.out.println("YES");
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc HashMap<Integer,Integer> A = new HashMap<>(); A new HashMap<>() for (int i = 0; i < N; i++){
            int a = sc.nextInt();
            if (A.containsKey(a)){
                System.out.println("NO");
                return;
            }
            A.put(a,0);
        } int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
            int a = sc.nextInt();
            if (A.containsKey(a)){
                System.out.println("NO");
                return;
            }
            A.put(a,0);
        } {
            int a = sc.nextInt();
            if (A.containsKey(a)){
                System.out.println("NO");
                return;
            }
            A.put(a,0);
        } int a = sc.nextInt(); a sc.nextInt() sc.nextInt sc if (A.containsKey(a)){
                System.out.println("NO");
                return;
            } A.containsKey(a) A.containsKey A a {
                System.out.println("NO");
                return;
            } System.out.println("NO") System.out.println System.out System System.out "NO" return; A.put(a,0) A.put A a 0 System.out.println("YES") System.out.println System.out System System.out "YES" String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        HashMap<Integer,Integer> A = new HashMap<>();
        for (int i = 0; i < N; i++){
            int a = sc.nextInt();
            if (A.containsKey(a)){
                System.out.println("NO");
                return;
            }
            A.put(a,0);
        }
        System.out.println("YES");
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        HashMap<Integer,Integer> A = new HashMap<>();
        for (int i = 0; i < N; i++){
            int a = sc.nextInt();
            if (A.containsKey(a)){
                System.out.println("NO");
                return;
            }
            A.put(a,0);
        }
        System.out.println("YES");
    }
} Main
import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        HashMap<Integer,Integer> A = new HashMap<>();
        for (int i = 0; i < N; i++){
            int a = sc.nextInt();
            if (A.containsKey(a)){
                System.out.println("NO");
                return;
            }
            A.put(a,0);
        }
        System.out.println("YES");
    }
}
