import java.util.*;
 
public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		HashSet<Integer> A = new HashSet<Integer>();

		for(int i=0; i<N; i++){
			A.add(sc.nextInt());
		}
		
		if(A.size()<N){
			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