import java.util.*;
import java.io.*;

public class Main {
	public static void main(String[] args) throws IOException {
		
		// 入出力高速化 java.io.* とthrows IOExceptionを忘れずに
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		
		int N = Integer.parseInt(br.readLine());
		String[] IN =br.readLine().split(" ") ; 
		
		String ans = "YES";
			
			HashMap<String,Integer> count = new HashMap<String,Integer>();
			for(int i=0; i<N; i++) {
				if (!count.containsKey(IN[i])){
					count.put(IN[i], 1); //まだHashMapにキーが登録されていないなら、登録する
				}else{//HashMapに既にキーがあるとき
					int now = count.get(IN[i]); //キーSに紐づく中身のintを取得
					count.replace(IN[i], now + 1);
				}
			}
			
			for(int key1:count.values()) {
				if(key1 > 1) {
					ans = "NO";
				}
			}
		
		System.out.println(ans);	
	}
}
/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