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 n = sc.nextInt();
		
		Set<Integer> set = new HashSet<>();
		for (int i = 0; i < n; i++) {
			int a = sc.nextInt();
			if (!set.add(a)) {
				System.out.println("NO");
				return;
			}
		}
		
		System.out.println("YES");
	}
} 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 n = sc.nextInt();
		
		Set<Integer> set = new HashSet<>();
		for (int i = 0; i < n; i++) {
			int a = sc.nextInt();
			if (!set.add(a)) {
				System.out.println("NO");
				return;
			}
		}
		
		System.out.println("YES");
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		
		Set<Integer> set = new HashSet<>();
		for (int i = 0; i < n; i++) {
			int a = sc.nextInt();
			if (!set.add(a)) {
				System.out.println("NO");
				return;
			}
		}
		
		System.out.println("YES");
	} main {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		
		Set<Integer> set = new HashSet<>();
		for (int i = 0; i < n; i++) {
			int a = sc.nextInt();
			if (!set.add(a)) {
				System.out.println("NO");
				return;
			}
		}
		
		System.out.println("YES");
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc Set<Integer> set = new HashSet<>(); set new HashSet<>() for (int i = 0; i < n; i++) {
			int a = sc.nextInt();
			if (!set.add(a)) {
				System.out.println("NO");
				return;
			}
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
			int a = sc.nextInt();
			if (!set.add(a)) {
				System.out.println("NO");
				return;
			}
		} {
			int a = sc.nextInt();
			if (!set.add(a)) {
				System.out.println("NO");
				return;
			}
		} int a = sc.nextInt(); a sc.nextInt() sc.nextInt sc if (!set.add(a)) {
				System.out.println("NO");
				return;
			} !set.add(a) set.add(a) set.add set a {
				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 sc = new Scanner(System.in);
		int n = sc.nextInt();
		
		Set<Integer> set = new HashSet<>();
		for (int i = 0; i < n; i++) {
			int a = sc.nextInt();
			if (!set.add(a)) {
				System.out.println("NO");
				return;
			}
		}
		
		System.out.println("YES");
	}
} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		
		Set<Integer> set = new HashSet<>();
		for (int i = 0; i < n; i++) {
			int a = sc.nextInt();
			if (!set.add(a)) {
				System.out.println("NO");
				return;
			}
		}
		
		System.out.println("YES");
	}
} 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 n = sc.nextInt();
		
		Set<Integer> set = new HashSet<>();
		for (int i = 0; i < n; i++) {
			int a = sc.nextInt();
			if (!set.add(a)) {
				System.out.println("NO");
				return;
			}
		}
		
		System.out.println("YES");
	}
}
