import java.util.*;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Collections;

public class Main {
	public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        Random rand = new Random();
        //ArrayList<Integer> list;
        List<Integer> list = new ArrayList<>(200000);
        
        int number = sc.nextInt();
        for(int i = 0; i < number ; i++){
            list.add(sc.nextInt());
        }

        Collections.sort(list);
        int count = 0;
        for(int i = 0; i < number - 1 ; i++){
            if(list.get(i).equals(list.get(i+1))){
                count++;
            }else{}
        }
        //System.out.println(list);

        if(count == 0){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
        


    
	}
} import java.util.*; util.* java import java.util.ArrayList; ArrayList java.util import java.util.Iterator; Iterator java.util import java.util.List; List java.util import java.util.Collections; Collections java.util public class Main {
	public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        Random rand = new Random();
        //ArrayList<Integer> list;
        List<Integer> list = new ArrayList<>(200000);
        
        int number = sc.nextInt();
        for(int i = 0; i < number ; i++){
            list.add(sc.nextInt());
        }

        Collections.sort(list);
        int count = 0;
        for(int i = 0; i < number - 1 ; i++){
            if(list.get(i).equals(list.get(i+1))){
                count++;
            }else{}
        }
        //System.out.println(list);

        if(count == 0){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
        


    
	}
} Main public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        Random rand = new Random();
        //ArrayList<Integer> list;
        List<Integer> list = new ArrayList<>(200000);
        
        int number = sc.nextInt();
        for(int i = 0; i < number ; i++){
            list.add(sc.nextInt());
        }

        Collections.sort(list);
        int count = 0;
        for(int i = 0; i < number - 1 ; i++){
            if(list.get(i).equals(list.get(i+1))){
                count++;
            }else{}
        }
        //System.out.println(list);

        if(count == 0){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
        


    
	} main {
        Scanner sc = new Scanner(System.in);
        Random rand = new Random();
        //ArrayList<Integer> list;
        List<Integer> list = new ArrayList<>(200000);
        
        int number = sc.nextInt();
        for(int i = 0; i < number ; i++){
            list.add(sc.nextInt());
        }

        Collections.sort(list);
        int count = 0;
        for(int i = 0; i < number - 1 ; i++){
            if(list.get(i).equals(list.get(i+1))){
                count++;
            }else{}
        }
        //System.out.println(list);

        if(count == 0){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
        


    
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) Random rand = new Random(); rand new Random() List<Integer> list = new ArrayList<>(200000); list new ArrayList<>(200000) int number = sc.nextInt(); number sc.nextInt() sc.nextInt sc for(int i = 0; i < number ; i++){
            list.add(sc.nextInt());
        } int i = 0; int i = 0; i 0 i < number i number i++ i++ i {
            list.add(sc.nextInt());
        } {
            list.add(sc.nextInt());
        } list.add(sc.nextInt()) list.add list sc.nextInt() sc.nextInt sc Collections.sort(list) Collections.sort Collections list int count = 0; count 0 for(int i = 0; i < number - 1 ; i++){
            if(list.get(i).equals(list.get(i+1))){
                count++;
            }else{}
        } int i = 0; int i = 0; i 0 i < number - 1 i number - 1 number 1 i++ i++ i {
            if(list.get(i).equals(list.get(i+1))){
                count++;
            }else{}
        } {
            if(list.get(i).equals(list.get(i+1))){
                count++;
            }else{}
        } if(list.get(i).equals(list.get(i+1))){
                count++;
            }else{} list.get(i).equals(list.get(i+1)) list.get(i).equals list.get(i) list.get list i list.get(i+1) list.get list i+1 i 1 {
                count++;
            } count++ count {} if(count == 0){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        } count == 0 count 0 {
            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);
        Random rand = new Random();
        //ArrayList<Integer> list;
        List<Integer> list = new ArrayList<>(200000);
        
        int number = sc.nextInt();
        for(int i = 0; i < number ; i++){
            list.add(sc.nextInt());
        }

        Collections.sort(list);
        int count = 0;
        for(int i = 0; i < number - 1 ; i++){
            if(list.get(i).equals(list.get(i+1))){
                count++;
            }else{}
        }
        //System.out.println(list);

        if(count == 0){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
        


    
	}
} public class Main {
	public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        Random rand = new Random();
        //ArrayList<Integer> list;
        List<Integer> list = new ArrayList<>(200000);
        
        int number = sc.nextInt();
        for(int i = 0; i < number ; i++){
            list.add(sc.nextInt());
        }

        Collections.sort(list);
        int count = 0;
        for(int i = 0; i < number - 1 ; i++){
            if(list.get(i).equals(list.get(i+1))){
                count++;
            }else{}
        }
        //System.out.println(list);

        if(count == 0){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
        


    
	}
} Main
import java.util.*;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Collections;

public class Main {
	public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        Random rand = new Random();
        //ArrayList<Integer> list;
        List<Integer> list = new ArrayList<>(200000);
        
        int number = sc.nextInt();
        for(int i = 0; i < number ; i++){
            list.add(sc.nextInt());
        }

        Collections.sort(list);
        int count = 0;
        for(int i = 0; i < number - 1 ; i++){
            if(list.get(i).equals(list.get(i+1))){
                count++;
            }else{}
        }
        //System.out.println(list);

        if(count == 0){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
        


    
	}
}