import java.util.*;
public class Main {
  /*
  private static void roop(int a, int b){
    for(int i = 0; i < a; i++){
      System.out.print(b);
    }
    System.out.println();
  }
  */
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    Set<Integer> set = new HashSet<Integer>();
    boolean flg = true;
    int tmp;
    for(int i = 0; i < n; i++){
      tmp = sc.nextInt();
      if(!set.contains(tmp)){
        set.add(tmp);
      }
      else
      {
        flg = false;
        break;
      }
    }
    //char[] a = sc.nextLine().toCharArray();
    
    if(flg)
    {
      System.out.println("YES");
    }
    else
    {
      System.out.println("NO");
    }
  }
} import java.util.*; util.* java public class Main {
  /*
  private static void roop(int a, int b){
    for(int i = 0; i < a; i++){
      System.out.print(b);
    }
    System.out.println();
  }
  */
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    Set<Integer> set = new HashSet<Integer>();
    boolean flg = true;
    int tmp;
    for(int i = 0; i < n; i++){
      tmp = sc.nextInt();
      if(!set.contains(tmp)){
        set.add(tmp);
      }
      else
      {
        flg = false;
        break;
      }
    }
    //char[] a = sc.nextLine().toCharArray();
    
    if(flg)
    {
      System.out.println("YES");
    }
    else
    {
      System.out.println("NO");
    }
  }
} Main /*
  private static void roop(int a, int b){
    for(int i = 0; i < a; i++){
      System.out.print(b);
    }
    System.out.println();
  }
  */
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    Set<Integer> set = new HashSet<Integer>();
    boolean flg = true;
    int tmp;
    for(int i = 0; i < n; i++){
      tmp = sc.nextInt();
      if(!set.contains(tmp)){
        set.add(tmp);
      }
      else
      {
        flg = false;
        break;
      }
    }
    //char[] a = sc.nextLine().toCharArray();
    
    if(flg)
    {
      System.out.println("YES");
    }
    else
    {
      System.out.println("NO");
    }
  } main {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    Set<Integer> set = new HashSet<Integer>();
    boolean flg = true;
    int tmp;
    for(int i = 0; i < n; i++){
      tmp = sc.nextInt();
      if(!set.contains(tmp)){
        set.add(tmp);
      }
      else
      {
        flg = false;
        break;
      }
    }
    //char[] a = sc.nextLine().toCharArray();
    
    if(flg)
    {
      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> set = new HashSet<Integer>(); set new HashSet<Integer>() boolean flg = true; flg true int tmp; tmp for(int i = 0; i < n; i++){
      tmp = sc.nextInt();
      if(!set.contains(tmp)){
        set.add(tmp);
      }
      else
      {
        flg = false;
        break;
      }
    } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
      tmp = sc.nextInt();
      if(!set.contains(tmp)){
        set.add(tmp);
      }
      else
      {
        flg = false;
        break;
      }
    } {
      tmp = sc.nextInt();
      if(!set.contains(tmp)){
        set.add(tmp);
      }
      else
      {
        flg = false;
        break;
      }
    } tmp = sc.nextInt() tmp sc.nextInt() sc.nextInt sc if(!set.contains(tmp)){
        set.add(tmp);
      }
      else
      {
        flg = false;
        break;
      } !set.contains(tmp) set.contains(tmp) set.contains set tmp {
        set.add(tmp);
      } set.add(tmp) set.add set tmp {
        flg = false;
        break;
      } flg = false flg false break; if(flg)
    {
      System.out.println("YES");
    }
    else
    {
      System.out.println("NO");
    } flg {
      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 public class Main {
  /*
  private static void roop(int a, int b){
    for(int i = 0; i < a; i++){
      System.out.print(b);
    }
    System.out.println();
  }
  */
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    Set<Integer> set = new HashSet<Integer>();
    boolean flg = true;
    int tmp;
    for(int i = 0; i < n; i++){
      tmp = sc.nextInt();
      if(!set.contains(tmp)){
        set.add(tmp);
      }
      else
      {
        flg = false;
        break;
      }
    }
    //char[] a = sc.nextLine().toCharArray();
    
    if(flg)
    {
      System.out.println("YES");
    }
    else
    {
      System.out.println("NO");
    }
  }
} public class Main {
  /*
  private static void roop(int a, int b){
    for(int i = 0; i < a; i++){
      System.out.print(b);
    }
    System.out.println();
  }
  */
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    Set<Integer> set = new HashSet<Integer>();
    boolean flg = true;
    int tmp;
    for(int i = 0; i < n; i++){
      tmp = sc.nextInt();
      if(!set.contains(tmp)){
        set.add(tmp);
      }
      else
      {
        flg = false;
        break;
      }
    }
    //char[] a = sc.nextLine().toCharArray();
    
    if(flg)
    {
      System.out.println("YES");
    }
    else
    {
      System.out.println("NO");
    }
  }
} Main
import java.util.*;
public class Main {
  /*
  private static void roop(int a, int b){
    for(int i = 0; i < a; i++){
      System.out.print(b);
    }
    System.out.println();
  }
  */
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    Set<Integer> set = new HashSet<Integer>();
    boolean flg = true;
    int tmp;
    for(int i = 0; i < n; i++){
      tmp = sc.nextInt();
      if(!set.contains(tmp)){
        set.add(tmp);
      }
      else
      {
        flg = false;
        break;
      }
    }
    //char[] a = sc.nextLine().toCharArray();
    
    if(flg)
    {
      System.out.println("YES");
    }
    else
    {
      System.out.println("NO");
    }
  }
}