import java.util.HashSet;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        HashSet<Integer> set = new HashSet<>();
        for (int i = 0; i < N; i++) {
           int num = sc.nextInt();
           if(set.contains(num)){
               System.out.println("NO");
               return;
           }
           set.add(num);
        }
        System.out.println("YES");
    }
} import java.util.HashSet; HashSet 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 N = sc.nextInt();
        HashSet<Integer> set = new HashSet<>();
        for (int i = 0; i < N; i++) {
           int num = sc.nextInt();
           if(set.contains(num)){
               System.out.println("NO");
               return;
           }
           set.add(num);
        }
        System.out.println("YES");
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        HashSet<Integer> set = new HashSet<>();
        for (int i = 0; i < N; i++) {
           int num = sc.nextInt();
           if(set.contains(num)){
               System.out.println("NO");
               return;
           }
           set.add(num);
        }
        System.out.println("YES");
    } main {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        HashSet<Integer> set = new HashSet<>();
        for (int i = 0; i < N; i++) {
           int num = sc.nextInt();
           if(set.contains(num)){
               System.out.println("NO");
               return;
           }
           set.add(num);
        }
        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 HashSet<Integer> set = new HashSet<>(); set new HashSet<>() for (int i = 0; i < N; i++) {
           int num = sc.nextInt();
           if(set.contains(num)){
               System.out.println("NO");
               return;
           }
           set.add(num);
        } int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
           int num = sc.nextInt();
           if(set.contains(num)){
               System.out.println("NO");
               return;
           }
           set.add(num);
        } {
           int num = sc.nextInt();
           if(set.contains(num)){
               System.out.println("NO");
               return;
           }
           set.add(num);
        } int num = sc.nextInt(); num sc.nextInt() sc.nextInt sc if(set.contains(num)){
               System.out.println("NO");
               return;
           } set.contains(num) set.contains set num {
               System.out.println("NO");
               return;
           } System.out.println("NO") System.out.println System.out System System.out "NO" return; set.add(num) set.add set num 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();
        HashSet<Integer> set = new HashSet<>();
        for (int i = 0; i < N; i++) {
           int num = sc.nextInt();
           if(set.contains(num)){
               System.out.println("NO");
               return;
           }
           set.add(num);
        }
        System.out.println("YES");
    }
} public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        HashSet<Integer> set = new HashSet<>();
        for (int i = 0; i < N; i++) {
           int num = sc.nextInt();
           if(set.contains(num)){
               System.out.println("NO");
               return;
           }
           set.add(num);
        }
        System.out.println("YES");
    }
} Main
import java.util.HashSet;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        HashSet<Integer> set = new HashSet<>();
        for (int i = 0; i < N; i++) {
           int num = sc.nextInt();
           if(set.contains(num)){
               System.out.println("NO");
               return;
           }
           set.add(num);
        }
        System.out.println("YES");
    }
}