import java.util.*;

public class Main {
    public static void main (String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] Az = new int[N];
        for (int i = 0; i < N; i++) {
            Az[i] = sc.nextInt();
        }
        HashSet<Integer> set = new HashSet<Integer>();
        for (int i = 0; i < N; i++) {
            set.add(Az[i]);
        }
        if (set.size() == N){
            System.out.println("YES");
        } else {
            System.out.println("NO");
        }
    }
}

/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