import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

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

public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int in_num = sc.nextInt();
        Map<Integer,Integer> m = new HashMap<>();
        for(int i = 0; i < in_num ;i++){
            int a = sc.nextInt();
            if(m.containsKey(a)){
                System.out.println("NO");
                return;
            }else{
                m.put(a, null);
            }
        }
        System.out.println("YES");
    }
}