import java.util.*;

class Main {
	Scanner sc;
	int N;
	Set<Integer> s;
	
	private void calc() {
		sc = new Scanner(System.in);
		N = sc.nextInt();
		s = new HashSet<Integer>(200000);
		boolean contains = false;
		for (int i = 0; i < N; i++) {
			if (!s.add(sc.nextInt())) contains = true;
		}
		System.out.println(contains?"NO":"YES");
	}

	public static void main(String[] args) {
		new Main().calc();
	}
} import java.util.*; util.* java class Main {
	Scanner sc;
	int N;
	Set<Integer> s;
	
	private void calc() {
		sc = new Scanner(System.in);
		N = sc.nextInt();
		s = new HashSet<Integer>(200000);
		boolean contains = false;
		for (int i = 0; i < N; i++) {
			if (!s.add(sc.nextInt())) contains = true;
		}
		System.out.println(contains?"NO":"YES");
	}

	public static void main(String[] args) {
		new Main().calc();
	}
} Main Scanner sc; sc int N; N Set<Integer> s; s private void calc() {
		sc = new Scanner(System.in);
		N = sc.nextInt();
		s = new HashSet<Integer>(200000);
		boolean contains = false;
		for (int i = 0; i < N; i++) {
			if (!s.add(sc.nextInt())) contains = true;
		}
		System.out.println(contains?"NO":"YES");
	} calc {
		sc = new Scanner(System.in);
		N = sc.nextInt();
		s = new HashSet<Integer>(200000);
		boolean contains = false;
		for (int i = 0; i < N; i++) {
			if (!s.add(sc.nextInt())) contains = true;
		}
		System.out.println(contains?"NO":"YES");
	} sc = new Scanner(System.in) sc new Scanner(System.in) N = sc.nextInt() N sc.nextInt() sc.nextInt sc s = new HashSet<Integer>(200000) s new HashSet<Integer>(200000) boolean contains = false; contains false for (int i = 0; i < N; i++) {
			if (!s.add(sc.nextInt())) contains = true;
		} int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
			if (!s.add(sc.nextInt())) contains = true;
		} {
			if (!s.add(sc.nextInt())) contains = true;
		} if (!s.add(sc.nextInt())) contains = true; !s.add(sc.nextInt()) s.add(sc.nextInt()) s.add s sc.nextInt() sc.nextInt sc contains = true contains true System.out.println(contains?"NO":"YES") System.out.println System.out System System.out contains?"NO":"YES" contains "NO" "YES" public static void main(String[] args) {
		new Main().calc();
	} main {
		new Main().calc();
	} new Main().calc() new Main().calc new Main() String[] args args
import java.util.*;

class Main {
	Scanner sc;
	int N;
	Set<Integer> s;
	
	private void calc() {
		sc = new Scanner(System.in);
		N = sc.nextInt();
		s = new HashSet<Integer>(200000);
		boolean contains = false;
		for (int i = 0; i < N; i++) {
			if (!s.add(sc.nextInt())) contains = true;
		}
		System.out.println(contains?"NO":"YES");
	}

	public static void main(String[] args) {
		new Main().calc();
	}
}
