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

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		Map<Integer, Integer> map = new HashMap<>();
		String result= "YES";
		int a;
		for(int i=0;i<n;i++) {
			a = sc.nextInt();
			if(map.containsKey(a)) {
				result = "NO";
				break;
			}else {
				map.put(a, 1);
			}
		}
		
		System.out.println(result);		
	}

} 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 sc = new Scanner(System.in);
		int n = sc.nextInt();
		Map<Integer, Integer> map = new HashMap<>();
		String result= "YES";
		int a;
		for(int i=0;i<n;i++) {
			a = sc.nextInt();
			if(map.containsKey(a)) {
				result = "NO";
				break;
			}else {
				map.put(a, 1);
			}
		}
		
		System.out.println(result);		
	}

} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		Map<Integer, Integer> map = new HashMap<>();
		String result= "YES";
		int a;
		for(int i=0;i<n;i++) {
			a = sc.nextInt();
			if(map.containsKey(a)) {
				result = "NO";
				break;
			}else {
				map.put(a, 1);
			}
		}
		
		System.out.println(result);		
	} main {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		Map<Integer, Integer> map = new HashMap<>();
		String result= "YES";
		int a;
		for(int i=0;i<n;i++) {
			a = sc.nextInt();
			if(map.containsKey(a)) {
				result = "NO";
				break;
			}else {
				map.put(a, 1);
			}
		}
		
		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 Map<Integer, Integer> map = new HashMap<>(); map new HashMap<>() String result= "YES"; result "YES" int a; a for(int i=0;i<n;i++) {
			a = sc.nextInt();
			if(map.containsKey(a)) {
				result = "NO";
				break;
			}else {
				map.put(a, 1);
			}
		} int i=0; int i=0; i 0 i<n i n i++ i++ i {
			a = sc.nextInt();
			if(map.containsKey(a)) {
				result = "NO";
				break;
			}else {
				map.put(a, 1);
			}
		} {
			a = sc.nextInt();
			if(map.containsKey(a)) {
				result = "NO";
				break;
			}else {
				map.put(a, 1);
			}
		} a = sc.nextInt() a sc.nextInt() sc.nextInt sc if(map.containsKey(a)) {
				result = "NO";
				break;
			}else {
				map.put(a, 1);
			} map.containsKey(a) map.containsKey map a {
				result = "NO";
				break;
			} result = "NO" result "NO" break; {
				map.put(a, 1);
			} map.put(a, 1) map.put map a 1 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();
		Map<Integer, Integer> map = new HashMap<>();
		String result= "YES";
		int a;
		for(int i=0;i<n;i++) {
			a = sc.nextInt();
			if(map.containsKey(a)) {
				result = "NO";
				break;
			}else {
				map.put(a, 1);
			}
		}
		
		System.out.println(result);		
	}

} public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		Map<Integer, Integer> map = new HashMap<>();
		String result= "YES";
		int a;
		for(int i=0;i<n;i++) {
			a = sc.nextInt();
			if(map.containsKey(a)) {
				result = "NO";
				break;
			}else {
				map.put(a, 1);
			}
		}
		
		System.out.println(result);		
	}

} Main

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

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		Map<Integer, Integer> map = new HashMap<>();
		String result= "YES";
		int a;
		for(int i=0;i<n;i++) {
			a = sc.nextInt();
			if(map.containsKey(a)) {
				result = "NO";
				break;
			}else {
				map.put(a, 1);
			}
		}
		
		System.out.println(result);		
	}

}
