import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int quantity = sc.nextInt();
        Set<Integer> numSet = new HashSet<>();
        
        String result = "YES";
        for (int i = 0; i < quantity; i++){
            if (!numSet.add(sc.nextInt())) {
                result = "NO";
                break;
            }
        }
        System.out.println(result);
    }

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

} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int quantity = sc.nextInt();
        Set<Integer> numSet = new HashSet<>();
        
        String result = "YES";
        for (int i = 0; i < quantity; i++){
            if (!numSet.add(sc.nextInt())) {
                result = "NO";
                break;
            }
        }
        System.out.println(result);
    } main {
        Scanner sc = new Scanner(System.in);
        int quantity = sc.nextInt();
        Set<Integer> numSet = new HashSet<>();
        
        String result = "YES";
        for (int i = 0; i < quantity; i++){
            if (!numSet.add(sc.nextInt())) {
                result = "NO";
                break;
            }
        }
        System.out.println(result);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int quantity = sc.nextInt(); quantity sc.nextInt() sc.nextInt sc Set<Integer> numSet = new HashSet<>(); numSet new HashSet<>() String result = "YES"; result "YES" for (int i = 0; i < quantity; i++){
            if (!numSet.add(sc.nextInt())) {
                result = "NO";
                break;
            }
        } int i = 0; int i = 0; i 0 i < quantity i quantity i++ i++ i {
            if (!numSet.add(sc.nextInt())) {
                result = "NO";
                break;
            }
        } {
            if (!numSet.add(sc.nextInt())) {
                result = "NO";
                break;
            }
        } if (!numSet.add(sc.nextInt())) {
                result = "NO";
                break;
            } !numSet.add(sc.nextInt()) numSet.add(sc.nextInt()) numSet.add numSet sc.nextInt() sc.nextInt sc {
                result = "NO";
                break;
            } result = "NO" result "NO" break; System.out.println(result) System.out.println System.out System System.out result String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int quantity = sc.nextInt();
        Set<Integer> numSet = new HashSet<>();
        
        String result = "YES";
        for (int i = 0; i < quantity; i++){
            if (!numSet.add(sc.nextInt())) {
                result = "NO";
                break;
            }
        }
        System.out.println(result);
    }

} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int quantity = sc.nextInt();
        Set<Integer> numSet = new HashSet<>();
        
        String result = "YES";
        for (int i = 0; i < quantity; i++){
            if (!numSet.add(sc.nextInt())) {
                result = "NO";
                break;
            }
        }
        System.out.println(result);
    }

} Main
import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int quantity = sc.nextInt();
        Set<Integer> numSet = new HashSet<>();
        
        String result = "YES";
        for (int i = 0; i < quantity; i++){
            if (!numSet.add(sc.nextInt())) {
                result = "NO";
                break;
            }
        }
        System.out.println(result);
    }

}