import java.util.*;

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

public class Main {
    public static void main(String[] args) throws Exception {
        
        Scanner scanner = new Scanner(System.in);
        
        int N = scanner.nextInt();
        boolean hantei = false;
        
        Map<Integer,Integer> map = new HashMap<Integer,Integer>();
        
        for(int i=0; i<N; i++){
            
            int x = scanner.nextInt();
            if(map.containsKey(x)){
                hantei = true;
            }else{
                map.put(x,1);
            }
            
        }
        
        if(hantei){
            System.out.println("NO");
        }else{
            System.out.println("YES");
        }
        
    }
}
