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