import java.util.Scanner;
import java.util.Arrays;

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

public class Main{
  public static void main(String[] args){
    Scanner scanner = new Scanner(System.in);
    
    int N = scanner.nextInt();
    int A[] = new int[N];
    for(int i = 0;i < N;i++){
      A[i] = scanner.nextInt();
    }
    Arrays.sort(A);
    String answer = "YES";
    for(int i = 0;i < N - 1;i++){
      if(A[i] == A[i + 1]) answer = "NO";
    }
    System.out.println(answer);
  }
}