import java.util.Arrays;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		int n  =  Integer.parseInt(sc.next());
		int a[] =  new int[n];
		for(int i = 0 ; i < n ; i++) {
			a[i] = Integer.parseInt(sc.next());
		}
		
		
		Arrays.sort(a);
		
		
		
		int tmp = a[0];
		String ans = "YES";
		for(int i = 1 ; i < n ; i++) {
			if(tmp == a[i]) {
				ans = "NO";
				break;
			}
			tmp = a[i];
		}
		
		
		
		System.out.println(ans);
	}




}
 import java.util.Arrays; Arrays 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  =  Integer.parseInt(sc.next());
		int a[] =  new int[n];
		for(int i = 0 ; i < n ; i++) {
			a[i] = Integer.parseInt(sc.next());
		}
		
		
		Arrays.sort(a);
		
		
		
		int tmp = a[0];
		String ans = "YES";
		for(int i = 1 ; i < n ; i++) {
			if(tmp == a[i]) {
				ans = "NO";
				break;
			}
			tmp = a[i];
		}
		
		
		
		System.out.println(ans);
	}




} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		int n  =  Integer.parseInt(sc.next());
		int a[] =  new int[n];
		for(int i = 0 ; i < n ; i++) {
			a[i] = Integer.parseInt(sc.next());
		}
		
		
		Arrays.sort(a);
		
		
		
		int tmp = a[0];
		String ans = "YES";
		for(int i = 1 ; i < n ; i++) {
			if(tmp == a[i]) {
				ans = "NO";
				break;
			}
			tmp = a[i];
		}
		
		
		
		System.out.println(ans);
	} main {
		Scanner sc = new Scanner(System.in);

		int n  =  Integer.parseInt(sc.next());
		int a[] =  new int[n];
		for(int i = 0 ; i < n ; i++) {
			a[i] = Integer.parseInt(sc.next());
		}
		
		
		Arrays.sort(a);
		
		
		
		int tmp = a[0];
		String ans = "YES";
		for(int i = 1 ; i < n ; i++) {
			if(tmp == a[i]) {
				ans = "NO";
				break;
			}
			tmp = a[i];
		}
		
		
		
		System.out.println(ans);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n  =  Integer.parseInt(sc.next()); n Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc int a[] =  new int[n]; a new int[n] n for(int i = 0 ; i < n ; i++) {
			a[i] = Integer.parseInt(sc.next());
		} int i = 0 ; int i = 0 ; i 0 i < n i n i++ i++ i {
			a[i] = Integer.parseInt(sc.next());
		} {
			a[i] = Integer.parseInt(sc.next());
		} a[i] = Integer.parseInt(sc.next()) a[i] a i Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc Arrays.sort(a) Arrays.sort Arrays a int tmp = a[0]; tmp a[0] a 0 String ans = "YES"; ans "YES" for(int i = 1 ; i < n ; i++) {
			if(tmp == a[i]) {
				ans = "NO";
				break;
			}
			tmp = a[i];
		} int i = 1 ; int i = 1 ; i 1 i < n i n i++ i++ i {
			if(tmp == a[i]) {
				ans = "NO";
				break;
			}
			tmp = a[i];
		} {
			if(tmp == a[i]) {
				ans = "NO";
				break;
			}
			tmp = a[i];
		} if(tmp == a[i]) {
				ans = "NO";
				break;
			} tmp == a[i] tmp a[i] a i {
				ans = "NO";
				break;
			} ans = "NO" ans "NO" break; tmp = a[i] tmp a[i] a i System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		int n  =  Integer.parseInt(sc.next());
		int a[] =  new int[n];
		for(int i = 0 ; i < n ; i++) {
			a[i] = Integer.parseInt(sc.next());
		}
		
		
		Arrays.sort(a);
		
		
		
		int tmp = a[0];
		String ans = "YES";
		for(int i = 1 ; i < n ; i++) {
			if(tmp == a[i]) {
				ans = "NO";
				break;
			}
			tmp = a[i];
		}
		
		
		
		System.out.println(ans);
	}




} public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		int n  =  Integer.parseInt(sc.next());
		int a[] =  new int[n];
		for(int i = 0 ; i < n ; i++) {
			a[i] = Integer.parseInt(sc.next());
		}
		
		
		Arrays.sort(a);
		
		
		
		int tmp = a[0];
		String ans = "YES";
		for(int i = 1 ; i < n ; i++) {
			if(tmp == a[i]) {
				ans = "NO";
				break;
			}
			tmp = a[i];
		}
		
		
		
		System.out.println(ans);
	}




} Main
import java.util.Arrays;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		int n  =  Integer.parseInt(sc.next());
		int a[] =  new int[n];
		for(int i = 0 ; i < n ; i++) {
			a[i] = Integer.parseInt(sc.next());
		}
		
		
		Arrays.sort(a);
		
		
		
		int tmp = a[0];
		String ans = "YES";
		for(int i = 1 ; i < n ; i++) {
			if(tmp == a[i]) {
				ans = "NO";
				break;
			}
			tmp = a[i];
		}
		
		
		
		System.out.println(ans);
	}




}

