import java.util.*;
public class Main{
  public static void main (String args[]){
    Scanner sc = new Scanner(System.in);
    
    int l = sc.nextInt();
    String ans = "YES";
    int[] list = new int[l];
    
    for(int i = 0; i < l; i++){
      list[i] = sc.nextInt();
    }
    
    Arrays.sort(list);
    
    for(int i = 0; i < l-1 ; i++){
      if(list[i]==list[i+1]){
        ans = "NO";
        break;
      }
    }
    
    System.out.println(ans);
    
  }
} import java.util.*; util.* java public class Main{
  public static void main (String args[]){
    Scanner sc = new Scanner(System.in);
    
    int l = sc.nextInt();
    String ans = "YES";
    int[] list = new int[l];
    
    for(int i = 0; i < l; i++){
      list[i] = sc.nextInt();
    }
    
    Arrays.sort(list);
    
    for(int i = 0; i < l-1 ; i++){
      if(list[i]==list[i+1]){
        ans = "NO";
        break;
      }
    }
    
    System.out.println(ans);
    
  }
} Main public static void main (String args[]){
    Scanner sc = new Scanner(System.in);
    
    int l = sc.nextInt();
    String ans = "YES";
    int[] list = new int[l];
    
    for(int i = 0; i < l; i++){
      list[i] = sc.nextInt();
    }
    
    Arrays.sort(list);
    
    for(int i = 0; i < l-1 ; i++){
      if(list[i]==list[i+1]){
        ans = "NO";
        break;
      }
    }
    
    System.out.println(ans);
    
  } main {
    Scanner sc = new Scanner(System.in);
    
    int l = sc.nextInt();
    String ans = "YES";
    int[] list = new int[l];
    
    for(int i = 0; i < l; i++){
      list[i] = sc.nextInt();
    }
    
    Arrays.sort(list);
    
    for(int i = 0; i < l-1 ; i++){
      if(list[i]==list[i+1]){
        ans = "NO";
        break;
      }
    }
    
    System.out.println(ans);
    
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int l = sc.nextInt(); l sc.nextInt() sc.nextInt sc String ans = "YES"; ans "YES" int[] list = new int[l]; list new int[l] l for(int i = 0; i < l; i++){
      list[i] = sc.nextInt();
    } int i = 0; int i = 0; i 0 i < l i l i++ i++ i {
      list[i] = sc.nextInt();
    } {
      list[i] = sc.nextInt();
    } list[i] = sc.nextInt() list[i] list i sc.nextInt() sc.nextInt sc Arrays.sort(list) Arrays.sort Arrays list for(int i = 0; i < l-1 ; i++){
      if(list[i]==list[i+1]){
        ans = "NO";
        break;
      }
    } int i = 0; int i = 0; i 0 i < l-1 i l-1 l 1 i++ i++ i {
      if(list[i]==list[i+1]){
        ans = "NO";
        break;
      }
    } {
      if(list[i]==list[i+1]){
        ans = "NO";
        break;
      }
    } if(list[i]==list[i+1]){
        ans = "NO";
        break;
      } list[i]==list[i+1] list[i] list i list[i+1] list i+1 i 1 {
        ans = "NO";
        break;
      } ans = "NO" ans "NO" break; System.out.println(ans) System.out.println System.out System System.out ans String args[] args public class Main{
  public static void main (String args[]){
    Scanner sc = new Scanner(System.in);
    
    int l = sc.nextInt();
    String ans = "YES";
    int[] list = new int[l];
    
    for(int i = 0; i < l; i++){
      list[i] = sc.nextInt();
    }
    
    Arrays.sort(list);
    
    for(int i = 0; i < l-1 ; i++){
      if(list[i]==list[i+1]){
        ans = "NO";
        break;
      }
    }
    
    System.out.println(ans);
    
  }
} public class Main{
  public static void main (String args[]){
    Scanner sc = new Scanner(System.in);
    
    int l = sc.nextInt();
    String ans = "YES";
    int[] list = new int[l];
    
    for(int i = 0; i < l; i++){
      list[i] = sc.nextInt();
    }
    
    Arrays.sort(list);
    
    for(int i = 0; i < l-1 ; i++){
      if(list[i]==list[i+1]){
        ans = "NO";
        break;
      }
    }
    
    System.out.println(ans);
    
  }
} Main
import java.util.*;
public class Main{
  public static void main (String args[]){
    Scanner sc = new Scanner(System.in);
    
    int l = sc.nextInt();
    String ans = "YES";
    int[] list = new int[l];
    
    for(int i = 0; i < l; i++){
      list[i] = sc.nextInt();
    }
    
    Arrays.sort(list);
    
    for(int i = 0; i < l-1 ; i++){
      if(list[i]==list[i+1]){
        ans = "NO";
        break;
      }
    }
    
    System.out.println(ans);
    
  }
}