import java.util.Map;
import java.util.Scanner;
import java.util.TreeMap;
public class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		int seisu = scan.nextInt();
		int count = 1;


		Map<String,Integer> hikaku = new TreeMap<String,Integer>();

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

			String suzi = scan.next();

			if(!hikaku.containsKey(suzi)) {

				count = 0;
				hikaku.put(suzi,count);
			}else {
				count = 1;
				hikaku.put(suzi, count);
			}
		}

		System.out.println(!hikaku.containsValue(1)?"YES":"NO");

		scan.close();

	}

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

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		int seisu = scan.nextInt();
		int count = 1;


		Map<String,Integer> hikaku = new TreeMap<String,Integer>();

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

			String suzi = scan.next();

			if(!hikaku.containsKey(suzi)) {

				count = 0;
				hikaku.put(suzi,count);
			}else {
				count = 1;
				hikaku.put(suzi, count);
			}
		}

		System.out.println(!hikaku.containsValue(1)?"YES":"NO");

		scan.close();

	}

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

		Scanner scan = new Scanner(System.in);

		int seisu = scan.nextInt();
		int count = 1;


		Map<String,Integer> hikaku = new TreeMap<String,Integer>();

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

			String suzi = scan.next();

			if(!hikaku.containsKey(suzi)) {

				count = 0;
				hikaku.put(suzi,count);
			}else {
				count = 1;
				hikaku.put(suzi, count);
			}
		}

		System.out.println(!hikaku.containsValue(1)?"YES":"NO");

		scan.close();

	} main {

		Scanner scan = new Scanner(System.in);

		int seisu = scan.nextInt();
		int count = 1;


		Map<String,Integer> hikaku = new TreeMap<String,Integer>();

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

			String suzi = scan.next();

			if(!hikaku.containsKey(suzi)) {

				count = 0;
				hikaku.put(suzi,count);
			}else {
				count = 1;
				hikaku.put(suzi, count);
			}
		}

		System.out.println(!hikaku.containsValue(1)?"YES":"NO");

		scan.close();

	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int seisu = scan.nextInt(); seisu scan.nextInt() scan.nextInt scan int count = 1; count 1 Map<String,Integer> hikaku = new TreeMap<String,Integer>(); hikaku new TreeMap<String,Integer>() for(int i=0;i<seisu;i++){

			String suzi = scan.next();

			if(!hikaku.containsKey(suzi)) {

				count = 0;
				hikaku.put(suzi,count);
			}else {
				count = 1;
				hikaku.put(suzi, count);
			}
		} int i=0; int i=0; i 0 i<seisu i seisu i++ i++ i {

			String suzi = scan.next();

			if(!hikaku.containsKey(suzi)) {

				count = 0;
				hikaku.put(suzi,count);
			}else {
				count = 1;
				hikaku.put(suzi, count);
			}
		} {

			String suzi = scan.next();

			if(!hikaku.containsKey(suzi)) {

				count = 0;
				hikaku.put(suzi,count);
			}else {
				count = 1;
				hikaku.put(suzi, count);
			}
		} String suzi = scan.next(); suzi scan.next() scan.next scan if(!hikaku.containsKey(suzi)) {

				count = 0;
				hikaku.put(suzi,count);
			}else {
				count = 1;
				hikaku.put(suzi, count);
			} !hikaku.containsKey(suzi) hikaku.containsKey(suzi) hikaku.containsKey hikaku suzi {

				count = 0;
				hikaku.put(suzi,count);
			} count = 0 count 0 hikaku.put(suzi,count) hikaku.put hikaku suzi count {
				count = 1;
				hikaku.put(suzi, count);
			} count = 1 count 1 hikaku.put(suzi, count) hikaku.put hikaku suzi count System.out.println(!hikaku.containsValue(1)?"YES":"NO") System.out.println System.out System System.out !hikaku.containsValue(1)?"YES":"NO" !hikaku.containsValue(1) hikaku.containsValue(1) hikaku.containsValue hikaku 1 "YES" "NO" scan.close() scan.close scan String[] args args public class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		int seisu = scan.nextInt();
		int count = 1;


		Map<String,Integer> hikaku = new TreeMap<String,Integer>();

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

			String suzi = scan.next();

			if(!hikaku.containsKey(suzi)) {

				count = 0;
				hikaku.put(suzi,count);
			}else {
				count = 1;
				hikaku.put(suzi, count);
			}
		}

		System.out.println(!hikaku.containsValue(1)?"YES":"NO");

		scan.close();

	}

} public class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		int seisu = scan.nextInt();
		int count = 1;


		Map<String,Integer> hikaku = new TreeMap<String,Integer>();

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

			String suzi = scan.next();

			if(!hikaku.containsKey(suzi)) {

				count = 0;
				hikaku.put(suzi,count);
			}else {
				count = 1;
				hikaku.put(suzi, count);
			}
		}

		System.out.println(!hikaku.containsValue(1)?"YES":"NO");

		scan.close();

	}

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

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		int seisu = scan.nextInt();
		int count = 1;


		Map<String,Integer> hikaku = new TreeMap<String,Integer>();

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

			String suzi = scan.next();

			if(!hikaku.containsKey(suzi)) {

				count = 0;
				hikaku.put(suzi,count);
			}else {
				count = 1;
				hikaku.put(suzi, count);
			}
		}

		System.out.println(!hikaku.containsValue(1)?"YES":"NO");

		scan.close();

	}

}
