import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.util.stream.Collectors;

public class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);
		int N = scan.nextInt();

		List<String> list = new ArrayList<>();

		for(int i = 0; i < N; i++) {
			list.add(scan.next());
		}

		List<String> fillteredList = list.stream().distinct().collect(Collectors.toList());

		if(fillteredList.size() == list.size()) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		}

	}
} import java.util.ArrayList; ArrayList java.util import java.util.List; List java.util import java.util.Scanner; Scanner java.util import java.util.stream.Collectors; Collectors java.util.stream public class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);
		int N = scan.nextInt();

		List<String> list = new ArrayList<>();

		for(int i = 0; i < N; i++) {
			list.add(scan.next());
		}

		List<String> fillteredList = list.stream().distinct().collect(Collectors.toList());

		if(fillteredList.size() == list.size()) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		}

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

		Scanner scan = new Scanner(System.in);
		int N = scan.nextInt();

		List<String> list = new ArrayList<>();

		for(int i = 0; i < N; i++) {
			list.add(scan.next());
		}

		List<String> fillteredList = list.stream().distinct().collect(Collectors.toList());

		if(fillteredList.size() == list.size()) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		}

	} main {

		Scanner scan = new Scanner(System.in);
		int N = scan.nextInt();

		List<String> list = new ArrayList<>();

		for(int i = 0; i < N; i++) {
			list.add(scan.next());
		}

		List<String> fillteredList = list.stream().distinct().collect(Collectors.toList());

		if(fillteredList.size() == list.size()) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		}

	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int N = scan.nextInt(); N scan.nextInt() scan.nextInt scan List<String> list = new ArrayList<>(); list new ArrayList<>() for(int i = 0; i < N; i++) {
			list.add(scan.next());
		} int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
			list.add(scan.next());
		} {
			list.add(scan.next());
		} list.add(scan.next()) list.add list scan.next() scan.next scan List<String> fillteredList = list.stream().distinct().collect(Collectors.toList()); fillteredList list.stream().distinct().collect(Collectors.toList()) list.stream().distinct().collect list.stream().distinct() list.stream().distinct list.stream() list.stream list Collectors.toList() Collectors.toList Collectors if(fillteredList.size() == list.size()) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		} fillteredList.size() == list.size() fillteredList.size() fillteredList.size fillteredList list.size() list.size list {
			System.out.println("YES");
		} System.out.println("YES") System.out.println System.out System System.out "YES" {
			System.out.println("NO");
		} System.out.println("NO") System.out.println System.out System System.out "NO" String[] args args public class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);
		int N = scan.nextInt();

		List<String> list = new ArrayList<>();

		for(int i = 0; i < N; i++) {
			list.add(scan.next());
		}

		List<String> fillteredList = list.stream().distinct().collect(Collectors.toList());

		if(fillteredList.size() == list.size()) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		}

	}
} public class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);
		int N = scan.nextInt();

		List<String> list = new ArrayList<>();

		for(int i = 0; i < N; i++) {
			list.add(scan.next());
		}

		List<String> fillteredList = list.stream().distinct().collect(Collectors.toList());

		if(fillteredList.size() == list.size()) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		}

	}
} Main
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.util.stream.Collectors;

public class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);
		int N = scan.nextInt();

		List<String> list = new ArrayList<>();

		for(int i = 0; i < N; i++) {
			list.add(scan.next());
		}

		List<String> fillteredList = list.stream().distinct().collect(Collectors.toList());

		if(fillteredList.size() == list.size()) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		}

	}
}