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