import java.util.*;
import java.io.*;
import java.math.*;
 
public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        boolean chk = true;
        HashMap<Integer,Integer> map = new HashMap<Integer,Integer>();
        for(int i = 0; i < n; i++){
            int a = sc.nextInt();
            if(map.containsKey(a)){
                chk = false;
                break;
            }else{
                map.put(a,1);
            }
        }
        if(chk){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
    }
} import java.util.*; util.* java import java.io.*; io.* java import java.math.*; math.* java public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        boolean chk = true;
        HashMap<Integer,Integer> map = new HashMap<Integer,Integer>();
        for(int i = 0; i < n; i++){
            int a = sc.nextInt();
            if(map.containsKey(a)){
                chk = false;
                break;
            }else{
                map.put(a,1);
            }
        }
        if(chk){
            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();
        boolean chk = true;
        HashMap<Integer,Integer> map = new HashMap<Integer,Integer>();
        for(int i = 0; i < n; i++){
            int a = sc.nextInt();
            if(map.containsKey(a)){
                chk = false;
                break;
            }else{
                map.put(a,1);
            }
        }
        if(chk){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
    } main {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        boolean chk = true;
        HashMap<Integer,Integer> map = new HashMap<Integer,Integer>();
        for(int i = 0; i < n; i++){
            int a = sc.nextInt();
            if(map.containsKey(a)){
                chk = false;
                break;
            }else{
                map.put(a,1);
            }
        }
        if(chk){
            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 boolean chk = true; chk true HashMap<Integer,Integer> map = new HashMap<Integer,Integer>(); map new HashMap<Integer,Integer>() for(int i = 0; i < n; i++){
            int a = sc.nextInt();
            if(map.containsKey(a)){
                chk = false;
                break;
            }else{
                map.put(a,1);
            }
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
            int a = sc.nextInt();
            if(map.containsKey(a)){
                chk = false;
                break;
            }else{
                map.put(a,1);
            }
        } {
            int a = sc.nextInt();
            if(map.containsKey(a)){
                chk = false;
                break;
            }else{
                map.put(a,1);
            }
        } int a = sc.nextInt(); a sc.nextInt() sc.nextInt sc if(map.containsKey(a)){
                chk = false;
                break;
            }else{
                map.put(a,1);
            } map.containsKey(a) map.containsKey map a {
                chk = false;
                break;
            } chk = false chk false break; {
                map.put(a,1);
            } map.put(a,1) map.put map a 1 if(chk){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        } chk {
            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();
        boolean chk = true;
        HashMap<Integer,Integer> map = new HashMap<Integer,Integer>();
        for(int i = 0; i < n; i++){
            int a = sc.nextInt();
            if(map.containsKey(a)){
                chk = false;
                break;
            }else{
                map.put(a,1);
            }
        }
        if(chk){
            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();
        boolean chk = true;
        HashMap<Integer,Integer> map = new HashMap<Integer,Integer>();
        for(int i = 0; i < n; i++){
            int a = sc.nextInt();
            if(map.containsKey(a)){
                chk = false;
                break;
            }else{
                map.put(a,1);
            }
        }
        if(chk){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
    }
} Main
import java.util.*;
import java.io.*;
import java.math.*;
 
public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        boolean chk = true;
        HashMap<Integer,Integer> map = new HashMap<Integer,Integer>();
        for(int i = 0; i < n; i++){
            int a = sc.nextInt();
            if(map.containsKey(a)){
                chk = false;
                break;
            }else{
                map.put(a,1);
            }
        }
        if(chk){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
    }
}