import java.util.HashSet;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long n = sc.nextLong();
        HashSet<Long> hs = new HashSet<>();
        long a = 0;
        boolean containFlag = false;
        for(int i = 0; i < n; i++){
            a = sc.nextLong();
            if(hs.contains(a)){
                containFlag = true;
            }
            hs.add(a);
        }
        if (!containFlag){
            System.out.println("YES");
        } else {
            System.out.println("NO");
        }
    }
} import java.util.HashSet; HashSet java.util import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long n = sc.nextLong();
        HashSet<Long> hs = new HashSet<>();
        long a = 0;
        boolean containFlag = false;
        for(int i = 0; i < n; i++){
            a = sc.nextLong();
            if(hs.contains(a)){
                containFlag = true;
            }
            hs.add(a);
        }
        if (!containFlag){
            System.out.println("YES");
        } else {
            System.out.println("NO");
        }
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long n = sc.nextLong();
        HashSet<Long> hs = new HashSet<>();
        long a = 0;
        boolean containFlag = false;
        for(int i = 0; i < n; i++){
            a = sc.nextLong();
            if(hs.contains(a)){
                containFlag = true;
            }
            hs.add(a);
        }
        if (!containFlag){
            System.out.println("YES");
        } else {
            System.out.println("NO");
        }
    } main {
        Scanner sc = new Scanner(System.in);
        long n = sc.nextLong();
        HashSet<Long> hs = new HashSet<>();
        long a = 0;
        boolean containFlag = false;
        for(int i = 0; i < n; i++){
            a = sc.nextLong();
            if(hs.contains(a)){
                containFlag = true;
            }
            hs.add(a);
        }
        if (!containFlag){
            System.out.println("YES");
        } else {
            System.out.println("NO");
        }
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long n = sc.nextLong(); n sc.nextLong() sc.nextLong sc HashSet<Long> hs = new HashSet<>(); hs new HashSet<>() long a = 0; a 0 boolean containFlag = false; containFlag false for(int i = 0; i < n; i++){
            a = sc.nextLong();
            if(hs.contains(a)){
                containFlag = true;
            }
            hs.add(a);
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
            a = sc.nextLong();
            if(hs.contains(a)){
                containFlag = true;
            }
            hs.add(a);
        } {
            a = sc.nextLong();
            if(hs.contains(a)){
                containFlag = true;
            }
            hs.add(a);
        } a = sc.nextLong() a sc.nextLong() sc.nextLong sc if(hs.contains(a)){
                containFlag = true;
            } hs.contains(a) hs.contains hs a {
                containFlag = true;
            } containFlag = true containFlag true hs.add(a) hs.add hs a if (!containFlag){
            System.out.println("YES");
        } else {
            System.out.println("NO");
        } !containFlag containFlag {
            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);
        long n = sc.nextLong();
        HashSet<Long> hs = new HashSet<>();
        long a = 0;
        boolean containFlag = false;
        for(int i = 0; i < n; i++){
            a = sc.nextLong();
            if(hs.contains(a)){
                containFlag = true;
            }
            hs.add(a);
        }
        if (!containFlag){
            System.out.println("YES");
        } else {
            System.out.println("NO");
        }
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long n = sc.nextLong();
        HashSet<Long> hs = new HashSet<>();
        long a = 0;
        boolean containFlag = false;
        for(int i = 0; i < n; i++){
            a = sc.nextLong();
            if(hs.contains(a)){
                containFlag = true;
            }
            hs.add(a);
        }
        if (!containFlag){
            System.out.println("YES");
        } else {
            System.out.println("NO");
        }
    }
} Main
import java.util.HashSet;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long n = sc.nextLong();
        HashSet<Long> hs = new HashSet<>();
        long a = 0;
        boolean containFlag = false;
        for(int i = 0; i < n; i++){
            a = sc.nextLong();
            if(hs.contains(a)){
                containFlag = true;
            }
            hs.add(a);
        }
        if (!containFlag){
            System.out.println("YES");
        } else {
            System.out.println("NO");
        }
    }
}