import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int num = sc.nextInt();
        String ans = "YES";
        Set<Integer> a = new HashSet<>();
        for(int i = 0; i < num; i++){
            a.add(sc.nextInt());
        }
        if(a.size() != num){
            ans = "NO";
        }
        
        System.out.println(ans);
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int num = sc.nextInt();
        String ans = "YES";
        Set<Integer> a = new HashSet<>();
        for(int i = 0; i < num; i++){
            a.add(sc.nextInt());
        }
        if(a.size() != num){
            ans = "NO";
        }
        
        System.out.println(ans);
    }
} Main public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int num = sc.nextInt();
        String ans = "YES";
        Set<Integer> a = new HashSet<>();
        for(int i = 0; i < num; i++){
            a.add(sc.nextInt());
        }
        if(a.size() != num){
            ans = "NO";
        }
        
        System.out.println(ans);
    } main {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int num = sc.nextInt();
        String ans = "YES";
        Set<Integer> a = new HashSet<>();
        for(int i = 0; i < num; i++){
            a.add(sc.nextInt());
        }
        if(a.size() != num){
            ans = "NO";
        }
        
        System.out.println(ans);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int num = sc.nextInt(); num sc.nextInt() sc.nextInt sc String ans = "YES"; ans "YES" Set<Integer> a = new HashSet<>(); a new HashSet<>() for(int i = 0; i < num; i++){
            a.add(sc.nextInt());
        } int i = 0; int i = 0; i 0 i < num i num i++ i++ i {
            a.add(sc.nextInt());
        } {
            a.add(sc.nextInt());
        } a.add(sc.nextInt()) a.add a sc.nextInt() sc.nextInt sc if(a.size() != num){
            ans = "NO";
        } a.size() != num a.size() a.size a num {
            ans = "NO";
        } ans = "NO" ans "NO" System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int num = sc.nextInt();
        String ans = "YES";
        Set<Integer> a = new HashSet<>();
        for(int i = 0; i < num; i++){
            a.add(sc.nextInt());
        }
        if(a.size() != num){
            ans = "NO";
        }
        
        System.out.println(ans);
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int num = sc.nextInt();
        String ans = "YES";
        Set<Integer> a = new HashSet<>();
        for(int i = 0; i < num; i++){
            a.add(sc.nextInt());
        }
        if(a.size() != num){
            ans = "NO";
        }
        
        System.out.println(ans);
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int num = sc.nextInt();
        String ans = "YES";
        Set<Integer> a = new HashSet<>();
        for(int i = 0; i < num; i++){
            a.add(sc.nextInt());
        }
        if(a.size() != num){
            ans = "NO";
        }
        
        System.out.println(ans);
    }
}