import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Main {
	public static void main (String args[]) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		Map<Long, Integer> map = new HashMap<Long, Integer>();
		for(int i = 0; i < n;i++){
			long a = scan.nextLong();
			if(map.get(a) == null) {
				map.put(a, 0);
			} else {
				System.out.println("NO");
				return;
			}
		}
		System.out.println("YES");
	}
} import java.util.HashMap; HashMap java.util import java.util.Map; Map 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();
		Map<Long, Integer> map = new HashMap<Long, Integer>();
		for(int i = 0; i < n;i++){
			long a = scan.nextLong();
			if(map.get(a) == null) {
				map.put(a, 0);
			} else {
				System.out.println("NO");
				return;
			}
		}
		System.out.println("YES");
	}
} Main public static void main (String args[]) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		Map<Long, Integer> map = new HashMap<Long, Integer>();
		for(int i = 0; i < n;i++){
			long a = scan.nextLong();
			if(map.get(a) == null) {
				map.put(a, 0);
			} else {
				System.out.println("NO");
				return;
			}
		}
		System.out.println("YES");
	} main {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		Map<Long, Integer> map = new HashMap<Long, Integer>();
		for(int i = 0; i < n;i++){
			long a = scan.nextLong();
			if(map.get(a) == null) {
				map.put(a, 0);
			} else {
				System.out.println("NO");
				return;
			}
		}
		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 Map<Long, Integer> map = new HashMap<Long, Integer>(); map new HashMap<Long, Integer>() for(int i = 0; i < n;i++){
			long a = scan.nextLong();
			if(map.get(a) == null) {
				map.put(a, 0);
			} else {
				System.out.println("NO");
				return;
			}
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
			long a = scan.nextLong();
			if(map.get(a) == null) {
				map.put(a, 0);
			} else {
				System.out.println("NO");
				return;
			}
		} {
			long a = scan.nextLong();
			if(map.get(a) == null) {
				map.put(a, 0);
			} else {
				System.out.println("NO");
				return;
			}
		} long a = scan.nextLong(); a scan.nextLong() scan.nextLong scan if(map.get(a) == null) {
				map.put(a, 0);
			} else {
				System.out.println("NO");
				return;
			} map.get(a) == null map.get(a) map.get map a null {
				map.put(a, 0);
			} map.put(a, 0) map.put map a 0 {
				System.out.println("NO");
				return;
			} System.out.println("NO") System.out.println System.out System System.out "NO" return; 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();
		Map<Long, Integer> map = new HashMap<Long, Integer>();
		for(int i = 0; i < n;i++){
			long a = scan.nextLong();
			if(map.get(a) == null) {
				map.put(a, 0);
			} else {
				System.out.println("NO");
				return;
			}
		}
		System.out.println("YES");
	}
} public class Main {
	public static void main (String args[]) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		Map<Long, Integer> map = new HashMap<Long, Integer>();
		for(int i = 0; i < n;i++){
			long a = scan.nextLong();
			if(map.get(a) == null) {
				map.put(a, 0);
			} else {
				System.out.println("NO");
				return;
			}
		}
		System.out.println("YES");
	}
} Main
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Main {
	public static void main (String args[]) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		Map<Long, Integer> map = new HashMap<Long, Integer>();
		for(int i = 0; i < n;i++){
			long a = scan.nextLong();
			if(map.get(a) == null) {
				map.put(a, 0);
			} else {
				System.out.println("NO");
				return;
			}
		}
		System.out.println("YES");
	}
}
