import java.util.*;

public class Main {

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

		int n = sc.nextInt();
		int[] num = new int[n];
		int chk = 0;
		
		for (int i = 0; i < n; i++) {
			num[i] = sc.nextInt();
		}
		
		Arrays.sort(num);
		

		for (int i = 0; i < n - 1; i++) {
			if (num[i] == num[i + 1]) {
				System.out.println("NO");
				chk++;
				break;
			}
		}
		
		if (chk == 0) {
			System.out.println("YES");
		}

	}

} import java.util.*; util.* java public class Main {

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

		int n = sc.nextInt();
		int[] num = new int[n];
		int chk = 0;
		
		for (int i = 0; i < n; i++) {
			num[i] = sc.nextInt();
		}
		
		Arrays.sort(num);
		

		for (int i = 0; i < n - 1; i++) {
			if (num[i] == num[i + 1]) {
				System.out.println("NO");
				chk++;
				break;
			}
		}
		
		if (chk == 0) {
			System.out.println("YES");
		}

	}

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

		int n = sc.nextInt();
		int[] num = new int[n];
		int chk = 0;
		
		for (int i = 0; i < n; i++) {
			num[i] = sc.nextInt();
		}
		
		Arrays.sort(num);
		

		for (int i = 0; i < n - 1; i++) {
			if (num[i] == num[i + 1]) {
				System.out.println("NO");
				chk++;
				break;
			}
		}
		
		if (chk == 0) {
			System.out.println("YES");
		}

	} main {
		Scanner sc = new Scanner(System.in);

		int n = sc.nextInt();
		int[] num = new int[n];
		int chk = 0;
		
		for (int i = 0; i < n; i++) {
			num[i] = sc.nextInt();
		}
		
		Arrays.sort(num);
		

		for (int i = 0; i < n - 1; i++) {
			if (num[i] == num[i + 1]) {
				System.out.println("NO");
				chk++;
				break;
			}
		}
		
		if (chk == 0) {
			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 int[] num = new int[n]; num new int[n] n int chk = 0; chk 0 for (int i = 0; i < n; i++) {
			num[i] = sc.nextInt();
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
			num[i] = sc.nextInt();
		} {
			num[i] = sc.nextInt();
		} num[i] = sc.nextInt() num[i] num i sc.nextInt() sc.nextInt sc Arrays.sort(num) Arrays.sort Arrays num for (int i = 0; i < n - 1; i++) {
			if (num[i] == num[i + 1]) {
				System.out.println("NO");
				chk++;
				break;
			}
		} int i = 0; int i = 0; i 0 i < n - 1 i n - 1 n 1 i++ i++ i {
			if (num[i] == num[i + 1]) {
				System.out.println("NO");
				chk++;
				break;
			}
		} {
			if (num[i] == num[i + 1]) {
				System.out.println("NO");
				chk++;
				break;
			}
		} if (num[i] == num[i + 1]) {
				System.out.println("NO");
				chk++;
				break;
			} num[i] == num[i + 1] num[i] num i num[i + 1] num i + 1 i 1 {
				System.out.println("NO");
				chk++;
				break;
			} System.out.println("NO") System.out.println System.out System System.out "NO" chk++ chk break; if (chk == 0) {
			System.out.println("YES");
		} chk == 0 chk 0 {
			System.out.println("YES");
		} 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();
		int[] num = new int[n];
		int chk = 0;
		
		for (int i = 0; i < n; i++) {
			num[i] = sc.nextInt();
		}
		
		Arrays.sort(num);
		

		for (int i = 0; i < n - 1; i++) {
			if (num[i] == num[i + 1]) {
				System.out.println("NO");
				chk++;
				break;
			}
		}
		
		if (chk == 0) {
			System.out.println("YES");
		}

	}

} public class Main {

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

		int n = sc.nextInt();
		int[] num = new int[n];
		int chk = 0;
		
		for (int i = 0; i < n; i++) {
			num[i] = sc.nextInt();
		}
		
		Arrays.sort(num);
		

		for (int i = 0; i < n - 1; i++) {
			if (num[i] == num[i + 1]) {
				System.out.println("NO");
				chk++;
				break;
			}
		}
		
		if (chk == 0) {
			System.out.println("YES");
		}

	}

} Main
import java.util.*;

public class Main {

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

		int n = sc.nextInt();
		int[] num = new int[n];
		int chk = 0;
		
		for (int i = 0; i < n; i++) {
			num[i] = sc.nextInt();
		}
		
		Arrays.sort(num);
		

		for (int i = 0; i < n - 1; i++) {
			if (num[i] == num[i + 1]) {
				System.out.println("NO");
				chk++;
				break;
			}
		}
		
		if (chk == 0) {
			System.out.println("YES");
		}

	}

}
