import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Scanner;
 

//result = Math.pow(num1, num3)
//StringBuffer str = new StringBuffer(hoge1);
//String hoge2 = str.reverse().toString();
public class Main {
	private static Scanner sc = new Scanner(System.in);
	static void p(String ans) {System.out.println(ans);};
	static void p(int ans) {System.out.println(ans);};
	static void p(long ans) {System.out.println(ans);};
	//static String eikomoji[]={"a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"};
	
	
	public static void main(String[] args) {
	int n=sc.nextInt();
	Map<Integer, Integer> map = new HashMap<Integer, Integer>(n);
	boolean a=true;
	for(int i=0;i<n&&a;i++) {
		int A = sc.nextInt();
		
		if(!map.containsKey(A)) {
			map.put(A,1);
		}else {
			a=false;
			
		}
	}
	//Map<String, Integer> map = new HashMap<String, Integer>(n);
	//ArrayList<String> cc = new ArrayList<>(n);
	if(a) {
		p("YES");
	}else {
		p("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