import java.util.*;
import java.lang.Math;
 
public class Main {
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    
    int N = sc.nextInt();
    
    int A[] = new int[N];
    
    for (int i = 0; i < N; i++) A[i] = sc.nextInt();
    
    Arrays.sort(A);
    
    boolean flg = false;
    
    for (int i = 0; i + 1 < N; i++) if (A[i] == A[i + 1]) flg = true;
    
    
    if (flg) {
      System.out.println("NO");
    } else {
      System.out.println("YES");
    }
  }
}
/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