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

public class Main{

	public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);
		int n = Integer.parseInt(scanner.nextLine());
		String[] temp = scanner.nextLine().split(" ");
		Map<Long, Long> map = new HashMap<Long,Long>();

		for(int i = 0; i < n; i++) {

			Long tmp = Long.parseLong(temp[i]);

			if(!map.containsKey(tmp)) {

				map.put(tmp, (long) 1);

			}else {

				System.out.println("NO");
				return;

			}

		}

		System.out.println("YES");

	}
} import java.util.HashMap; HashMap java.util import java.util.Map; Map java.util import java.util.Scanner; Scanner java.util public class Main{

	public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);
		int n = Integer.parseInt(scanner.nextLine());
		String[] temp = scanner.nextLine().split(" ");
		Map<Long, Long> map = new HashMap<Long,Long>();

		for(int i = 0; i < n; i++) {

			Long tmp = Long.parseLong(temp[i]);

			if(!map.containsKey(tmp)) {

				map.put(tmp, (long) 1);

			}else {

				System.out.println("NO");
				return;

			}

		}

		System.out.println("YES");

	}
} Main public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);
		int n = Integer.parseInt(scanner.nextLine());
		String[] temp = scanner.nextLine().split(" ");
		Map<Long, Long> map = new HashMap<Long,Long>();

		for(int i = 0; i < n; i++) {

			Long tmp = Long.parseLong(temp[i]);

			if(!map.containsKey(tmp)) {

				map.put(tmp, (long) 1);

			}else {

				System.out.println("NO");
				return;

			}

		}

		System.out.println("YES");

	} main {

		Scanner scanner = new Scanner(System.in);
		int n = Integer.parseInt(scanner.nextLine());
		String[] temp = scanner.nextLine().split(" ");
		Map<Long, Long> map = new HashMap<Long,Long>();

		for(int i = 0; i < n; i++) {

			Long tmp = Long.parseLong(temp[i]);

			if(!map.containsKey(tmp)) {

				map.put(tmp, (long) 1);

			}else {

				System.out.println("NO");
				return;

			}

		}

		System.out.println("YES");

	} Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) int n = Integer.parseInt(scanner.nextLine()); n Integer.parseInt(scanner.nextLine()) Integer.parseInt Integer scanner.nextLine() scanner.nextLine scanner String[] temp = scanner.nextLine().split(" "); temp scanner.nextLine().split(" ") scanner.nextLine().split scanner.nextLine() scanner.nextLine scanner " " Map<Long, Long> map = new HashMap<Long,Long>(); map new HashMap<Long,Long>() for(int i = 0; i < n; i++) {

			Long tmp = Long.parseLong(temp[i]);

			if(!map.containsKey(tmp)) {

				map.put(tmp, (long) 1);

			}else {

				System.out.println("NO");
				return;

			}

		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {

			Long tmp = Long.parseLong(temp[i]);

			if(!map.containsKey(tmp)) {

				map.put(tmp, (long) 1);

			}else {

				System.out.println("NO");
				return;

			}

		} {

			Long tmp = Long.parseLong(temp[i]);

			if(!map.containsKey(tmp)) {

				map.put(tmp, (long) 1);

			}else {

				System.out.println("NO");
				return;

			}

		} Long tmp = Long.parseLong(temp[i]); tmp Long.parseLong(temp[i]) Long.parseLong Long temp[i] temp i if(!map.containsKey(tmp)) {

				map.put(tmp, (long) 1);

			}else {

				System.out.println("NO");
				return;

			} !map.containsKey(tmp) map.containsKey(tmp) map.containsKey map tmp {

				map.put(tmp, (long) 1);

			} map.put(tmp, (long) 1) map.put map tmp (long) 1 {

				System.out.println("NO");
				return;

			} System.out.println("NO") System.out.println System.out System System.out "NO" return; System.out.println("YES") System.out.println System.out System System.out "YES" String[] args args public class Main{

	public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);
		int n = Integer.parseInt(scanner.nextLine());
		String[] temp = scanner.nextLine().split(" ");
		Map<Long, Long> map = new HashMap<Long,Long>();

		for(int i = 0; i < n; i++) {

			Long tmp = Long.parseLong(temp[i]);

			if(!map.containsKey(tmp)) {

				map.put(tmp, (long) 1);

			}else {

				System.out.println("NO");
				return;

			}

		}

		System.out.println("YES");

	}
} public class Main{

	public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);
		int n = Integer.parseInt(scanner.nextLine());
		String[] temp = scanner.nextLine().split(" ");
		Map<Long, Long> map = new HashMap<Long,Long>();

		for(int i = 0; i < n; i++) {

			Long tmp = Long.parseLong(temp[i]);

			if(!map.containsKey(tmp)) {

				map.put(tmp, (long) 1);

			}else {

				System.out.println("NO");
				return;

			}

		}

		System.out.println("YES");

	}
} Main
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Main{

	public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);
		int n = Integer.parseInt(scanner.nextLine());
		String[] temp = scanner.nextLine().split(" ");
		Map<Long, Long> map = new HashMap<Long,Long>();

		for(int i = 0; i < n; i++) {

			Long tmp = Long.parseLong(temp[i]);

			if(!map.containsKey(tmp)) {

				map.put(tmp, (long) 1);

			}else {

				System.out.println("NO");
				return;

			}

		}

		System.out.println("YES");

	}
}