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

class Main {
    public static void main(String[] args) {
        Scanner stdIn = new Scanner(System.in);
        int n = stdIn.nextInt();
        HashSet<Integer> set = new HashSet<Integer>();

        for (int i = 0; i < n; i++) {
            set.add(stdIn.nextInt());
        }

        if (set.size() == n) {
            System.out.println("YES");
        } else {
            System.out.println("NO");
        }
    }
} import java.util.HashSet; HashSet java.util import java.util.Scanner; Scanner java.util class Main {
    public static void main(String[] args) {
        Scanner stdIn = new Scanner(System.in);
        int n = stdIn.nextInt();
        HashSet<Integer> set = new HashSet<Integer>();

        for (int i = 0; i < n; i++) {
            set.add(stdIn.nextInt());
        }

        if (set.size() == n) {
            System.out.println("YES");
        } else {
            System.out.println("NO");
        }
    }
} Main public static void main(String[] args) {
        Scanner stdIn = new Scanner(System.in);
        int n = stdIn.nextInt();
        HashSet<Integer> set = new HashSet<Integer>();

        for (int i = 0; i < n; i++) {
            set.add(stdIn.nextInt());
        }

        if (set.size() == n) {
            System.out.println("YES");
        } else {
            System.out.println("NO");
        }
    } main {
        Scanner stdIn = new Scanner(System.in);
        int n = stdIn.nextInt();
        HashSet<Integer> set = new HashSet<Integer>();

        for (int i = 0; i < n; i++) {
            set.add(stdIn.nextInt());
        }

        if (set.size() == n) {
            System.out.println("YES");
        } else {
            System.out.println("NO");
        }
    } Scanner stdIn = new Scanner(System.in); stdIn new Scanner(System.in) int n = stdIn.nextInt(); n stdIn.nextInt() stdIn.nextInt stdIn HashSet<Integer> set = new HashSet<Integer>(); set new HashSet<Integer>() for (int i = 0; i < n; i++) {
            set.add(stdIn.nextInt());
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
            set.add(stdIn.nextInt());
        } {
            set.add(stdIn.nextInt());
        } set.add(stdIn.nextInt()) set.add set stdIn.nextInt() stdIn.nextInt stdIn if (set.size() == n) {
            System.out.println("YES");
        } else {
            System.out.println("NO");
        } set.size() == n set.size() set.size set n {
            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
import java.util.HashSet;
import java.util.Scanner;

class Main {
    public static void main(String[] args) {
        Scanner stdIn = new Scanner(System.in);
        int n = stdIn.nextInt();
        HashSet<Integer> set = new HashSet<Integer>();

        for (int i = 0; i < n; i++) {
            set.add(stdIn.nextInt());
        }

        if (set.size() == n) {
            System.out.println("YES");
        } else {
            System.out.println("NO");
        }
    }
}
