import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        
        Scanner scanner = new Scanner(System.in);
        
        int N = scanner.nextInt();
        boolean hantei = false;
        
        Map<Integer,Integer> map = new HashMap<Integer,Integer>();
        
        for(int i=0; i<N; i++){
            
            int x = scanner.nextInt();
            if(map.containsKey(x)){
                hantei = true;
            }else{
                map.put(x,1);
            }
            
        }
        
        if(hantei){
            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