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