import java.io.*; 
import java.lang.*;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.*;
class Main{
public static void main(String[] args){
try{
   BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        String b = reader.readLine();
   String c = reader.readLine();
  String parts[] = c.split(" ");
 	int n = Integer.parseInt(b);
  Arrays.sort(parts);
   int flag = 0;
  for(int i =0;i<n-1;i++){
  	if(parts[i].compareTo(parts[i+1]) == 0){
      flag =1;
      System.out.println("NO");
      i = n;
    }
  }
  
 
  
  if(flag == 0){
    System.out.println("YES");
  }
}catch(Exception e){}
}
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz