import java.util.Scanner;
import java.util.HashSet;

public class Main{
    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);

        int N = scanner.nextInt();
        HashSet<Long> list = new HashSet<Long>();

        for(int i = 0; i < N; i++) {
            list.add(scanner.nextLong());
        }
        
        if(N == list.size()){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
	}
} import java.util.Scanner; Scanner java.util import java.util.HashSet; HashSet java.util public class Main{
    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);

        int N = scanner.nextInt();
        HashSet<Long> list = new HashSet<Long>();

        for(int i = 0; i < N; i++) {
            list.add(scanner.nextLong());
        }
        
        if(N == list.size()){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
	}
} Main public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);

        int N = scanner.nextInt();
        HashSet<Long> list = new HashSet<Long>();

        for(int i = 0; i < N; i++) {
            list.add(scanner.nextLong());
        }
        
        if(N == list.size()){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
	} main {
        Scanner scanner = new Scanner(System.in);

        int N = scanner.nextInt();
        HashSet<Long> list = new HashSet<Long>();

        for(int i = 0; i < N; i++) {
            list.add(scanner.nextLong());
        }
        
        if(N == list.size()){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
	} Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) int N = scanner.nextInt(); N scanner.nextInt() scanner.nextInt scanner HashSet<Long> list = new HashSet<Long>(); list new HashSet<Long>() for(int i = 0; i < N; i++) {
            list.add(scanner.nextLong());
        } int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
            list.add(scanner.nextLong());
        } {
            list.add(scanner.nextLong());
        } list.add(scanner.nextLong()) list.add list scanner.nextLong() scanner.nextLong scanner if(N == list.size()){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        } N == list.size() N 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 scanner = new Scanner(System.in);

        int N = scanner.nextInt();
        HashSet<Long> list = new HashSet<Long>();

        for(int i = 0; i < N; i++) {
            list.add(scanner.nextLong());
        }
        
        if(N == list.size()){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
	}
} public class Main{
    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);

        int N = scanner.nextInt();
        HashSet<Long> list = new HashSet<Long>();

        for(int i = 0; i < N; i++) {
            list.add(scanner.nextLong());
        }
        
        if(N == list.size()){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
	}
} Main
import java.util.Scanner;
import java.util.HashSet;

public class Main{
    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);

        int N = scanner.nextInt();
        HashSet<Long> list = new HashSet<Long>();

        for(int i = 0; i < N; i++) {
            list.add(scanner.nextLong());
        }
        
        if(N == list.size()){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
	}
}