import java.util.Scanner;
import java.util.HashSet;
public class Main{
  public static void main(String[] args){
	Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    HashSet<Long> set = new HashSet<Long>();
    boolean hantei = true;
    
    for(int i=0; i<N; i++){
      int bSize = set.size();
      Long A = sc.nextLong();
      if(set.contains(A) == true){
        hantei = false;
        break;
      } else set.add(A);
    }
    if(hantei == true) System.out.println("YES");
    else System.out.println("NO");
  }
} import java.util.Scanner; Scanner java.util import java.util.HashSet; HashSet java.util public class Main{
  public static void main(String[] args){
	Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    HashSet<Long> set = new HashSet<Long>();
    boolean hantei = true;
    
    for(int i=0; i<N; i++){
      int bSize = set.size();
      Long A = sc.nextLong();
      if(set.contains(A) == true){
        hantei = false;
        break;
      } else set.add(A);
    }
    if(hantei == true) 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();
    HashSet<Long> set = new HashSet<Long>();
    boolean hantei = true;
    
    for(int i=0; i<N; i++){
      int bSize = set.size();
      Long A = sc.nextLong();
      if(set.contains(A) == true){
        hantei = false;
        break;
      } else set.add(A);
    }
    if(hantei == true) System.out.println("YES");
    else System.out.println("NO");
  } main {
	Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    HashSet<Long> set = new HashSet<Long>();
    boolean hantei = true;
    
    for(int i=0; i<N; i++){
      int bSize = set.size();
      Long A = sc.nextLong();
      if(set.contains(A) == true){
        hantei = false;
        break;
      } else set.add(A);
    }
    if(hantei == true) 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 HashSet<Long> set = new HashSet<Long>(); set new HashSet<Long>() boolean hantei = true; hantei true for(int i=0; i<N; i++){
      int bSize = set.size();
      Long A = sc.nextLong();
      if(set.contains(A) == true){
        hantei = false;
        break;
      } else set.add(A);
    } int i=0; int i=0; i 0 i<N i N i++ i++ i {
      int bSize = set.size();
      Long A = sc.nextLong();
      if(set.contains(A) == true){
        hantei = false;
        break;
      } else set.add(A);
    } {
      int bSize = set.size();
      Long A = sc.nextLong();
      if(set.contains(A) == true){
        hantei = false;
        break;
      } else set.add(A);
    } int bSize = set.size(); bSize set.size() set.size set Long A = sc.nextLong(); A sc.nextLong() sc.nextLong sc if(set.contains(A) == true){
        hantei = false;
        break;
      } else set.add(A); set.contains(A) == true set.contains(A) set.contains set A true {
        hantei = false;
        break;
      } hantei = false hantei false break; set.add(A) set.add set A if(hantei == true) System.out.println("YES");
    else System.out.println("NO"); hantei == true hantei true System.out.println("YES") System.out.println System.out System System.out "YES" System.out.println("NO") System.out.println 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();
    HashSet<Long> set = new HashSet<Long>();
    boolean hantei = true;
    
    for(int i=0; i<N; i++){
      int bSize = set.size();
      Long A = sc.nextLong();
      if(set.contains(A) == true){
        hantei = false;
        break;
      } else set.add(A);
    }
    if(hantei == true) System.out.println("YES");
    else System.out.println("NO");
  }
} public class Main{
  public static void main(String[] args){
	Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    HashSet<Long> set = new HashSet<Long>();
    boolean hantei = true;
    
    for(int i=0; i<N; i++){
      int bSize = set.size();
      Long A = sc.nextLong();
      if(set.contains(A) == true){
        hantei = false;
        break;
      } else set.add(A);
    }
    if(hantei == true) System.out.println("YES");
    else System.out.println("NO");
  }
} Main
import java.util.Scanner;
import java.util.HashSet;
public class Main{
  public static void main(String[] args){
	Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    HashSet<Long> set = new HashSet<Long>();
    boolean hantei = true;
    
    for(int i=0; i<N; i++){
      int bSize = set.size();
      Long A = sc.nextLong();
      if(set.contains(A) == true){
        hantei = false;
        break;
      } else set.add(A);
    }
    if(hantei == true) System.out.println("YES");
    else System.out.println("NO");
  }
}
