import java.util.*;


public class Main {
  public static void main(String[] args) {

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

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

    Scanner sc = new Scanner(System.in);
    String ans = "";
    int N = sc.nextInt();
    int[] A = new int[N];
    for(int i = 0;i < N;i++){
      A[i] = sc.nextInt();
    }
    Arrays.sort(A);
    for(int i = 0;i < N-1;i++){
      if(A[i] == A[i+1]){
        ans = "NO";
        break;
      }else{
        ans = "YES";
      }
    }
    System.out.print(ans);
  } main {

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

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

    Scanner sc = new Scanner(System.in);
    String ans = "";
    int N = sc.nextInt();
    int[] A = new int[N];
    for(int i = 0;i < N;i++){
      A[i] = sc.nextInt();
    }
    Arrays.sort(A);
    for(int i = 0;i < N-1;i++){
      if(A[i] == A[i+1]){
        ans = "NO";
        break;
      }else{
        ans = "YES";
      }
    }
    System.out.print(ans);
  }
} Main
import java.util.*;


public class Main {
  public static void main(String[] args) {

    Scanner sc = new Scanner(System.in);
    String ans = "";
    int N = sc.nextInt();
    int[] A = new int[N];
    for(int i = 0;i < N;i++){
      A[i] = sc.nextInt();
    }
    Arrays.sort(A);
    for(int i = 0;i < N-1;i++){
      if(A[i] == A[i+1]){
        ans = "NO";
        break;
      }else{
        ans = "YES";
      }
    }
    System.out.print(ans);
  }
}
