import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		HashSet<Integer> set = new HashSet<>();
		String result = "YES";
		for (int i = 0; i < n; i++) {
			int num = sc.nextInt();
			if (set.contains(num)) {
				result = "NO";
				break;
			}
			set.add(num);
		}
		sc.close();
		System.out.println(result);
	}
} import java.util.ArrayList; ArrayList java.util import java.util.HashSet; HashSet java.util import java.util.List; List java.util import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		HashSet<Integer> set = new HashSet<>();
		String result = "YES";
		for (int i = 0; i < n; i++) {
			int num = sc.nextInt();
			if (set.contains(num)) {
				result = "NO";
				break;
			}
			set.add(num);
		}
		sc.close();
		System.out.println(result);
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		HashSet<Integer> set = new HashSet<>();
		String result = "YES";
		for (int i = 0; i < n; i++) {
			int num = sc.nextInt();
			if (set.contains(num)) {
				result = "NO";
				break;
			}
			set.add(num);
		}
		sc.close();
		System.out.println(result);
	} main {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		HashSet<Integer> set = new HashSet<>();
		String result = "YES";
		for (int i = 0; i < n; i++) {
			int num = sc.nextInt();
			if (set.contains(num)) {
				result = "NO";
				break;
			}
			set.add(num);
		}
		sc.close();
		System.out.println(result);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc HashSet<Integer> set = new HashSet<>(); set new HashSet<>() String result = "YES"; result "YES" for (int i = 0; i < n; i++) {
			int num = sc.nextInt();
			if (set.contains(num)) {
				result = "NO";
				break;
			}
			set.add(num);
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
			int num = sc.nextInt();
			if (set.contains(num)) {
				result = "NO";
				break;
			}
			set.add(num);
		} {
			int num = sc.nextInt();
			if (set.contains(num)) {
				result = "NO";
				break;
			}
			set.add(num);
		} int num = sc.nextInt(); num sc.nextInt() sc.nextInt sc if (set.contains(num)) {
				result = "NO";
				break;
			} set.contains(num) set.contains set num {
				result = "NO";
				break;
			} result = "NO" result "NO" break; set.add(num) set.add set num sc.close() sc.close sc System.out.println(result) System.out.println System.out System System.out result String[] args args public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		HashSet<Integer> set = new HashSet<>();
		String result = "YES";
		for (int i = 0; i < n; i++) {
			int num = sc.nextInt();
			if (set.contains(num)) {
				result = "NO";
				break;
			}
			set.add(num);
		}
		sc.close();
		System.out.println(result);
	}
} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		HashSet<Integer> set = new HashSet<>();
		String result = "YES";
		for (int i = 0; i < n; i++) {
			int num = sc.nextInt();
			if (set.contains(num)) {
				result = "NO";
				break;
			}
			set.add(num);
		}
		sc.close();
		System.out.println(result);
	}
} Main
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Scanner;

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