import java.util.*;

public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Map<Integer,Boolean> map = new HashMap<>();
        String ans = "YES";
        for(int i = 0;i<n;i++){
            int num = sc.nextInt();
            if(map.get(num) == null){
                map.put(num, true);
            }else{
                ans = "NO";
                break;
            }
        }
        System.out.println(ans);
    }
} import java.util.*; util.* java public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Map<Integer,Boolean> map = new HashMap<>();
        String ans = "YES";
        for(int i = 0;i<n;i++){
            int num = sc.nextInt();
            if(map.get(num) == null){
                map.put(num, true);
            }else{
                ans = "NO";
                break;
            }
        }
        System.out.println(ans);
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Map<Integer,Boolean> map = new HashMap<>();
        String ans = "YES";
        for(int i = 0;i<n;i++){
            int num = sc.nextInt();
            if(map.get(num) == null){
                map.put(num, true);
            }else{
                ans = "NO";
                break;
            }
        }
        System.out.println(ans);
    } main {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Map<Integer,Boolean> map = new HashMap<>();
        String ans = "YES";
        for(int i = 0;i<n;i++){
            int num = sc.nextInt();
            if(map.get(num) == null){
                map.put(num, true);
            }else{
                ans = "NO";
                break;
            }
        }
        System.out.println(ans);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc Map<Integer,Boolean> map = new HashMap<>(); map new HashMap<>() String ans = "YES"; ans "YES" for(int i = 0;i<n;i++){
            int num = sc.nextInt();
            if(map.get(num) == null){
                map.put(num, true);
            }else{
                ans = "NO";
                break;
            }
        } int i = 0; int i = 0; i 0 i<n i n i++ i++ i {
            int num = sc.nextInt();
            if(map.get(num) == null){
                map.put(num, true);
            }else{
                ans = "NO";
                break;
            }
        } {
            int num = sc.nextInt();
            if(map.get(num) == null){
                map.put(num, true);
            }else{
                ans = "NO";
                break;
            }
        } int num = sc.nextInt(); num sc.nextInt() sc.nextInt sc if(map.get(num) == null){
                map.put(num, true);
            }else{
                ans = "NO";
                break;
            } map.get(num) == null map.get(num) map.get map num null {
                map.put(num, true);
            } map.put(num, true) map.put map num true {
                ans = "NO";
                break;
            } ans = "NO" ans "NO" break; 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) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Map<Integer,Boolean> map = new HashMap<>();
        String ans = "YES";
        for(int i = 0;i<n;i++){
            int num = sc.nextInt();
            if(map.get(num) == null){
                map.put(num, true);
            }else{
                ans = "NO";
                break;
            }
        }
        System.out.println(ans);
    }
} public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Map<Integer,Boolean> map = new HashMap<>();
        String ans = "YES";
        for(int i = 0;i<n;i++){
            int num = sc.nextInt();
            if(map.get(num) == null){
                map.put(num, true);
            }else{
                ans = "NO";
                break;
            }
        }
        System.out.println(ans);
    }
} Main
import java.util.*;

public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Map<Integer,Boolean> map = new HashMap<>();
        String ans = "YES";
        for(int i = 0;i<n;i++){
            int num = sc.nextInt();
            if(map.get(num) == null){
                map.put(num, true);
            }else{
                ans = "NO";
                break;
            }
        }
        System.out.println(ans);
    }
}