import java.util.*;
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);
        
        for(int i=1; i<n; i++){
            if(a[i]==a[i-1]){
                System.out.println("NO");
                return;
            }
        }
        
        
        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