import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Map<Integer,Integer> a = new HashMap<>();
        String ret = "YES";
        for(int i=0; i<n; i++){
            Integer wk = sc.nextInt();
            if(a.containsKey(wk)){
				ret = "NO";
                break;
            }else{
                a.put(wk,wk);
              
            }
        }
       System.out.println(ret);
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Map<Integer,Integer> a = new HashMap<>();
        String ret = "YES";
        for(int i=0; i<n; i++){
            Integer wk = sc.nextInt();
            if(a.containsKey(wk)){
				ret = "NO";
                break;
            }else{
                a.put(wk,wk);
              
            }
        }
       System.out.println(ret);
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Map<Integer,Integer> a = new HashMap<>();
        String ret = "YES";
        for(int i=0; i<n; i++){
            Integer wk = sc.nextInt();
            if(a.containsKey(wk)){
				ret = "NO";
                break;
            }else{
                a.put(wk,wk);
              
            }
        }
       System.out.println(ret);
    } main {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Map<Integer,Integer> a = new HashMap<>();
        String ret = "YES";
        for(int i=0; i<n; i++){
            Integer wk = sc.nextInt();
            if(a.containsKey(wk)){
				ret = "NO";
                break;
            }else{
                a.put(wk,wk);
              
            }
        }
       System.out.println(ret);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc Map<Integer,Integer> a = new HashMap<>(); a new HashMap<>() String ret = "YES"; ret "YES" for(int i=0; i<n; i++){
            Integer wk = sc.nextInt();
            if(a.containsKey(wk)){
				ret = "NO";
                break;
            }else{
                a.put(wk,wk);
              
            }
        } int i=0; int i=0; i 0 i<n i n i++ i++ i {
            Integer wk = sc.nextInt();
            if(a.containsKey(wk)){
				ret = "NO";
                break;
            }else{
                a.put(wk,wk);
              
            }
        } {
            Integer wk = sc.nextInt();
            if(a.containsKey(wk)){
				ret = "NO";
                break;
            }else{
                a.put(wk,wk);
              
            }
        } Integer wk = sc.nextInt(); wk sc.nextInt() sc.nextInt sc if(a.containsKey(wk)){
				ret = "NO";
                break;
            }else{
                a.put(wk,wk);
              
            } a.containsKey(wk) a.containsKey a wk {
				ret = "NO";
                break;
            } ret = "NO" ret "NO" break; {
                a.put(wk,wk);
              
            } a.put(wk,wk) a.put a wk wk System.out.println(ret) System.out.println System.out System System.out ret String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Map<Integer,Integer> a = new HashMap<>();
        String ret = "YES";
        for(int i=0; i<n; i++){
            Integer wk = sc.nextInt();
            if(a.containsKey(wk)){
				ret = "NO";
                break;
            }else{
                a.put(wk,wk);
              
            }
        }
       System.out.println(ret);
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Map<Integer,Integer> a = new HashMap<>();
        String ret = "YES";
        for(int i=0; i<n; i++){
            Integer wk = sc.nextInt();
            if(a.containsKey(wk)){
				ret = "NO";
                break;
            }else{
                a.put(wk,wk);
              
            }
        }
       System.out.println(ret);
    }
} Main
import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Map<Integer,Integer> a = new HashMap<>();
        String ret = "YES";
        for(int i=0; i<n; i++){
            Integer wk = sc.nextInt();
            if(a.containsKey(wk)){
				ret = "NO";
                break;
            }else{
                a.put(wk,wk);
              
            }
        }
       System.out.println(ret);
    }
}