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

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int len = sc.nextInt();
		int count = 0;
		Set<Integer> number = new HashSet<Integer>();
		while (count < len) {
			number.add(sc.nextInt());
			count++;
		}
		if (number.size() == len) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
	}
} import java.util.HashSet; HashSet java.util import java.util.Scanner; Scanner java.util import java.util.Set; Set java.util public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int len = sc.nextInt();
		int count = 0;
		Set<Integer> number = new HashSet<Integer>();
		while (count < len) {
			number.add(sc.nextInt());
			count++;
		}
		if (number.size() == len) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int len = sc.nextInt();
		int count = 0;
		Set<Integer> number = new HashSet<Integer>();
		while (count < len) {
			number.add(sc.nextInt());
			count++;
		}
		if (number.size() == len) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
	} main {
		Scanner sc = new Scanner(System.in);
		int len = sc.nextInt();
		int count = 0;
		Set<Integer> number = new HashSet<Integer>();
		while (count < len) {
			number.add(sc.nextInt());
			count++;
		}
		if (number.size() == len) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int len = sc.nextInt(); len sc.nextInt() sc.nextInt sc int count = 0; count 0 Set<Integer> number = new HashSet<Integer>(); number new HashSet<Integer>() while (count < len) {
			number.add(sc.nextInt());
			count++;
		} count < len count len {
			number.add(sc.nextInt());
			count++;
		} number.add(sc.nextInt()) number.add number sc.nextInt() sc.nextInt sc count++ count if (number.size() == len) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		} number.size() == len number.size() number.size number len {
			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);
		int len = sc.nextInt();
		int count = 0;
		Set<Integer> number = new HashSet<Integer>();
		while (count < len) {
			number.add(sc.nextInt());
			count++;
		}
		if (number.size() == len) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
	}
} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int len = sc.nextInt();
		int count = 0;
		Set<Integer> number = new HashSet<Integer>();
		while (count < len) {
			number.add(sc.nextInt());
			count++;
		}
		if (number.size() == len) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
	}
} Main
import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int len = sc.nextInt();
		int count = 0;
		Set<Integer> number = new HashSet<Integer>();
		while (count < len) {
			number.add(sc.nextInt());
			count++;
		}
		if (number.size() == len) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
	}
}
