//package atcoder;
 
import java.util.*;
import java.math.BigDecimal;
 
public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		Set<String> set = new HashSet<>();
		for(int i=0;i<N;i++) {
			set.add(sc.next());
		}
		if(set.size() == N) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		}
	}
} import java.util.*; util.* java import java.math.BigDecimal; BigDecimal java.math public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		Set<String> set = new HashSet<>();
		for(int i=0;i<N;i++) {
			set.add(sc.next());
		}
		if(set.size() == N) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		}
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		Set<String> set = new HashSet<>();
		for(int i=0;i<N;i++) {
			set.add(sc.next());
		}
		if(set.size() == N) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		}
	} main {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		Set<String> set = new HashSet<>();
		for(int i=0;i<N;i++) {
			set.add(sc.next());
		}
		if(set.size() == N) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		}
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc Set<String> set = new HashSet<>(); set new HashSet<>() for(int i=0;i<N;i++) {
			set.add(sc.next());
		} int i=0; int i=0; i 0 i<N i N i++ i++ i {
			set.add(sc.next());
		} {
			set.add(sc.next());
		} set.add(sc.next()) set.add set sc.next() sc.next sc if(set.size() == N) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		} set.size() == N set.size() set.size set N {
			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 sc = new Scanner(System.in);
		int N = sc.nextInt();
		Set<String> set = new HashSet<>();
		for(int i=0;i<N;i++) {
			set.add(sc.next());
		}
		if(set.size() == N) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		}
	}
} public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		Set<String> set = new HashSet<>();
		for(int i=0;i<N;i++) {
			set.add(sc.next());
		}
		if(set.size() == N) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		}
	}
} Main
//package atcoder;
 
import java.util.*;
import java.math.BigDecimal;
 
public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		Set<String> set = new HashSet<>();
		for(int i=0;i<N;i++) {
			set.add(sc.next());
		}
		if(set.size() == N) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		}
	}
}
