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

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		HashSet<Long> list = new HashSet<Long>();
		boolean check = true;
		long in = 0;

		for(int i = 0;i < n;i++) {
			in = scan.nextLong();
			if(list.contains(in)) {
				check = false;
			}
			list.add(in);
		}

		if(!check) {
			System.out.println("NO");
		}else {
			System.out.println("YES");
		}
	}
} import java.util.HashSet; HashSet java.util import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		HashSet<Long> list = new HashSet<Long>();
		boolean check = true;
		long in = 0;

		for(int i = 0;i < n;i++) {
			in = scan.nextLong();
			if(list.contains(in)) {
				check = false;
			}
			list.add(in);
		}

		if(!check) {
			System.out.println("NO");
		}else {
			System.out.println("YES");
		}
	}
} Main public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		HashSet<Long> list = new HashSet<Long>();
		boolean check = true;
		long in = 0;

		for(int i = 0;i < n;i++) {
			in = scan.nextLong();
			if(list.contains(in)) {
				check = false;
			}
			list.add(in);
		}

		if(!check) {
			System.out.println("NO");
		}else {
			System.out.println("YES");
		}
	} main {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		HashSet<Long> list = new HashSet<Long>();
		boolean check = true;
		long in = 0;

		for(int i = 0;i < n;i++) {
			in = scan.nextLong();
			if(list.contains(in)) {
				check = false;
			}
			list.add(in);
		}

		if(!check) {
			System.out.println("NO");
		}else {
			System.out.println("YES");
		}
	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int n = scan.nextInt(); n scan.nextInt() scan.nextInt scan HashSet<Long> list = new HashSet<Long>(); list new HashSet<Long>() boolean check = true; check true long in = 0; in 0 for(int i = 0;i < n;i++) {
			in = scan.nextLong();
			if(list.contains(in)) {
				check = false;
			}
			list.add(in);
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
			in = scan.nextLong();
			if(list.contains(in)) {
				check = false;
			}
			list.add(in);
		} {
			in = scan.nextLong();
			if(list.contains(in)) {
				check = false;
			}
			list.add(in);
		} in = scan.nextLong() in scan.nextLong() scan.nextLong scan if(list.contains(in)) {
				check = false;
			} list.contains(in) list.contains list in {
				check = false;
			} check = false check false list.add(in) list.add list in if(!check) {
			System.out.println("NO");
		}else {
			System.out.println("YES");
		} !check check {
			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) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		HashSet<Long> list = new HashSet<Long>();
		boolean check = true;
		long in = 0;

		for(int i = 0;i < n;i++) {
			in = scan.nextLong();
			if(list.contains(in)) {
				check = false;
			}
			list.add(in);
		}

		if(!check) {
			System.out.println("NO");
		}else {
			System.out.println("YES");
		}
	}
} public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		HashSet<Long> list = new HashSet<Long>();
		boolean check = true;
		long in = 0;

		for(int i = 0;i < n;i++) {
			in = scan.nextLong();
			if(list.contains(in)) {
				check = false;
			}
			list.add(in);
		}

		if(!check) {
			System.out.println("NO");
		}else {
			System.out.println("YES");
		}
	}
} Main
import java.util.HashSet;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		HashSet<Long> list = new HashSet<Long>();
		boolean check = true;
		long in = 0;

		for(int i = 0;i < n;i++) {
			in = scan.nextLong();
			if(list.contains(in)) {
				check = false;
			}
			list.add(in);
		}

		if(!check) {
			System.out.println("NO");
		}else {
			System.out.println("YES");
		}
	}
}