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);
  }
}
/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