import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;
 
public class Main {
 
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		Set<Integer> c = new HashSet<>();
		for(int i=0;i<n;i++){
			c.add(sc.nextInt());
		}
		sc.close();
		if(n==c.size()){
			System.out.println("YES");
		}else{
			System.out.println("NO");
		}
	}
} import java.util.HashSet; HashSet java.util import java.util.Scanner; Scanner java.util import java.util.Set; Set java.util public class Main {
 
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		Set<Integer> c = new HashSet<>();
		for(int i=0;i<n;i++){
			c.add(sc.nextInt());
		}
		sc.close();
		if(n==c.size()){
			System.out.println("YES");
		}else{
			System.out.println("NO");
		}
	}
} Main public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		Set<Integer> c = new HashSet<>();
		for(int i=0;i<n;i++){
			c.add(sc.nextInt());
		}
		sc.close();
		if(n==c.size()){
			System.out.println("YES");
		}else{
			System.out.println("NO");
		}
	} main {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		Set<Integer> c = new HashSet<>();
		for(int i=0;i<n;i++){
			c.add(sc.nextInt());
		}
		sc.close();
		if(n==c.size()){
			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<Integer> c = new HashSet<>(); c new HashSet<>() for(int i=0;i<n;i++){
			c.add(sc.nextInt());
		} int i=0; int i=0; i 0 i<n i n i++ i++ i {
			c.add(sc.nextInt());
		} {
			c.add(sc.nextInt());
		} c.add(sc.nextInt()) c.add c sc.nextInt() sc.nextInt sc sc.close() sc.close sc if(n==c.size()){
			System.out.println("YES");
		}else{
			System.out.println("NO");
		} n==c.size() n c.size() c.size c {
			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) throws Exception {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		Set<Integer> c = new HashSet<>();
		for(int i=0;i<n;i++){
			c.add(sc.nextInt());
		}
		sc.close();
		if(n==c.size()){
			System.out.println("YES");
		}else{
			System.out.println("NO");
		}
	}
} public class Main {
 
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		Set<Integer> c = new HashSet<>();
		for(int i=0;i<n;i++){
			c.add(sc.nextInt());
		}
		sc.close();
		if(n==c.size()){
			System.out.println("YES");
		}else{
			System.out.println("NO");
		}
	}
} Main
import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;
 
public class Main {
 
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		Set<Integer> c = new HashSet<>();
		for(int i=0;i<n;i++){
			c.add(sc.nextInt());
		}
		sc.close();
		if(n==c.size()){
			System.out.println("YES");
		}else{
			System.out.println("NO");
		}
	}
}