import java.util.*;

public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int n = scan.nextInt();
    HashSet<Integer> g = new HashSet<Integer>();
    for (int i=0;i<n;i++){
      g.add(scan.nextInt());
    }

    if (g.size() < n){
      System.out.println("NO");
    }
    else{
      System.out.println("YES");
    }
  }
} import java.util.*; util.* java public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int n = scan.nextInt();
    HashSet<Integer> g = new HashSet<Integer>();
    for (int i=0;i<n;i++){
      g.add(scan.nextInt());
    }

    if (g.size() < n){
      System.out.println("NO");
    }
    else{
      System.out.println("YES");
    }
  }
} Main public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int n = scan.nextInt();
    HashSet<Integer> g = new HashSet<Integer>();
    for (int i=0;i<n;i++){
      g.add(scan.nextInt());
    }

    if (g.size() < n){
      System.out.println("NO");
    }
    else{
      System.out.println("YES");
    }
  } main {
    Scanner scan = new Scanner(System.in);
    int n = scan.nextInt();
    HashSet<Integer> g = new HashSet<Integer>();
    for (int i=0;i<n;i++){
      g.add(scan.nextInt());
    }

    if (g.size() < n){
      System.out.println("NO");
    }
    else{
      System.out.println("YES");
    }
  } Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int n = scan.nextInt(); n scan.nextInt() scan.nextInt scan HashSet<Integer> g = new HashSet<Integer>(); g new HashSet<Integer>() for (int i=0;i<n;i++){
      g.add(scan.nextInt());
    } int i=0; int i=0; i 0 i<n i n i++ i++ i {
      g.add(scan.nextInt());
    } {
      g.add(scan.nextInt());
    } g.add(scan.nextInt()) g.add g scan.nextInt() scan.nextInt scan if (g.size() < n){
      System.out.println("NO");
    }
    else{
      System.out.println("YES");
    } g.size() < n g.size() g.size g n {
      System.out.println("NO");
    } System.out.println("NO") System.out.println System.out System System.out "NO" {
      System.out.println("YES");
    } 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 scan = new Scanner(System.in);
    int n = scan.nextInt();
    HashSet<Integer> g = new HashSet<Integer>();
    for (int i=0;i<n;i++){
      g.add(scan.nextInt());
    }

    if (g.size() < n){
      System.out.println("NO");
    }
    else{
      System.out.println("YES");
    }
  }
} public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int n = scan.nextInt();
    HashSet<Integer> g = new HashSet<Integer>();
    for (int i=0;i<n;i++){
      g.add(scan.nextInt());
    }

    if (g.size() < n){
      System.out.println("NO");
    }
    else{
      System.out.println("YES");
    }
  }
} Main
import java.util.*;

public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int n = scan.nextInt();
    HashSet<Integer> g = new HashSet<Integer>();
    for (int i=0;i<n;i++){
      g.add(scan.nextInt());
    }

    if (g.size() < n){
      System.out.println("NO");
    }
    else{
      System.out.println("YES");
    }
  }
}
