import java.util.HashMap;
import java.util.Scanner;

public class Main
{
	public static void main(String[] args)
	{
		HashMap<String,String> map = new HashMap<String,String>();

		Scanner scan = new Scanner(System.in);
		String str = scan.nextLine();
		int n = Integer.parseInt(str);

		str = scan.nextLine();
		String[] substr = str.split(" ", 0);
		String ans = "YES";
		for (int i=0; i<n; i++) {
			if (map.containsKey(substr[i])) {
				ans = "NO";
				break;
			}  else {
				map.put(substr[i], "1");
			}
		}

		System.out.println(ans);
	}
} import java.util.HashMap; HashMap java.util import java.util.Scanner; Scanner java.util public class Main
{
	public static void main(String[] args)
	{
		HashMap<String,String> map = new HashMap<String,String>();

		Scanner scan = new Scanner(System.in);
		String str = scan.nextLine();
		int n = Integer.parseInt(str);

		str = scan.nextLine();
		String[] substr = str.split(" ", 0);
		String ans = "YES";
		for (int i=0; i<n; i++) {
			if (map.containsKey(substr[i])) {
				ans = "NO";
				break;
			}  else {
				map.put(substr[i], "1");
			}
		}

		System.out.println(ans);
	}
} Main public static void main(String[] args)
	{
		HashMap<String,String> map = new HashMap<String,String>();

		Scanner scan = new Scanner(System.in);
		String str = scan.nextLine();
		int n = Integer.parseInt(str);

		str = scan.nextLine();
		String[] substr = str.split(" ", 0);
		String ans = "YES";
		for (int i=0; i<n; i++) {
			if (map.containsKey(substr[i])) {
				ans = "NO";
				break;
			}  else {
				map.put(substr[i], "1");
			}
		}

		System.out.println(ans);
	} main {
		HashMap<String,String> map = new HashMap<String,String>();

		Scanner scan = new Scanner(System.in);
		String str = scan.nextLine();
		int n = Integer.parseInt(str);

		str = scan.nextLine();
		String[] substr = str.split(" ", 0);
		String ans = "YES";
		for (int i=0; i<n; i++) {
			if (map.containsKey(substr[i])) {
				ans = "NO";
				break;
			}  else {
				map.put(substr[i], "1");
			}
		}

		System.out.println(ans);
	} HashMap<String,String> map = new HashMap<String,String>(); map new HashMap<String,String>() Scanner scan = new Scanner(System.in); scan new Scanner(System.in) String str = scan.nextLine(); str scan.nextLine() scan.nextLine scan int n = Integer.parseInt(str); n Integer.parseInt(str) Integer.parseInt Integer str str = scan.nextLine() str scan.nextLine() scan.nextLine scan String[] substr = str.split(" ", 0); substr str.split(" ", 0) str.split str " " 0 String ans = "YES"; ans "YES" for (int i=0; i<n; i++) {
			if (map.containsKey(substr[i])) {
				ans = "NO";
				break;
			}  else {
				map.put(substr[i], "1");
			}
		} int i=0; int i=0; i 0 i<n i n i++ i++ i {
			if (map.containsKey(substr[i])) {
				ans = "NO";
				break;
			}  else {
				map.put(substr[i], "1");
			}
		} {
			if (map.containsKey(substr[i])) {
				ans = "NO";
				break;
			}  else {
				map.put(substr[i], "1");
			}
		} if (map.containsKey(substr[i])) {
				ans = "NO";
				break;
			}  else {
				map.put(substr[i], "1");
			} map.containsKey(substr[i]) map.containsKey map substr[i] substr i {
				ans = "NO";
				break;
			} ans = "NO" ans "NO" break; {
				map.put(substr[i], "1");
			} map.put(substr[i], "1") map.put map substr[i] substr i "1" System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main
{
	public static void main(String[] args)
	{
		HashMap<String,String> map = new HashMap<String,String>();

		Scanner scan = new Scanner(System.in);
		String str = scan.nextLine();
		int n = Integer.parseInt(str);

		str = scan.nextLine();
		String[] substr = str.split(" ", 0);
		String ans = "YES";
		for (int i=0; i<n; i++) {
			if (map.containsKey(substr[i])) {
				ans = "NO";
				break;
			}  else {
				map.put(substr[i], "1");
			}
		}

		System.out.println(ans);
	}
} public class Main
{
	public static void main(String[] args)
	{
		HashMap<String,String> map = new HashMap<String,String>();

		Scanner scan = new Scanner(System.in);
		String str = scan.nextLine();
		int n = Integer.parseInt(str);

		str = scan.nextLine();
		String[] substr = str.split(" ", 0);
		String ans = "YES";
		for (int i=0; i<n; i++) {
			if (map.containsKey(substr[i])) {
				ans = "NO";
				break;
			}  else {
				map.put(substr[i], "1");
			}
		}

		System.out.println(ans);
	}
} Main
import java.util.HashMap;
import java.util.Scanner;

public class Main
{
	public static void main(String[] args)
	{
		HashMap<String,String> map = new HashMap<String,String>();

		Scanner scan = new Scanner(System.in);
		String str = scan.nextLine();
		int n = Integer.parseInt(str);

		str = scan.nextLine();
		String[] substr = str.split(" ", 0);
		String ans = "YES";
		for (int i=0; i<n; i++) {
			if (map.containsKey(substr[i])) {
				ans = "NO";
				break;
			}  else {
				map.put(substr[i], "1");
			}
		}

		System.out.println(ans);
	}
}