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

class Main {
	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		int N = scanner.nextInt();
		int[] A = new int[N];
		for (int i = 0; i < N; i++) {
			A[i] = scanner.nextInt();
		}

		Arrays.sort(A);

		boolean flag = false;
		for (int i = 0; i < N - 1; i++) {
			if (A[i] == A[i + 1]) {
				flag = true;
				break;
			}
		}

		if (flag) {
			System.out.println("NO");
		}
		else {
			System.out.println("YES");
		}
	}
} import java.util.Scanner; Scanner java.util import java.util.Arrays; Arrays java.util class Main {
	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		int N = scanner.nextInt();
		int[] A = new int[N];
		for (int i = 0; i < N; i++) {
			A[i] = scanner.nextInt();
		}

		Arrays.sort(A);

		boolean flag = false;
		for (int i = 0; i < N - 1; i++) {
			if (A[i] == A[i + 1]) {
				flag = true;
				break;
			}
		}

		if (flag) {
			System.out.println("NO");
		}
		else {
			System.out.println("YES");
		}
	}
} Main public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		int N = scanner.nextInt();
		int[] A = new int[N];
		for (int i = 0; i < N; i++) {
			A[i] = scanner.nextInt();
		}

		Arrays.sort(A);

		boolean flag = false;
		for (int i = 0; i < N - 1; i++) {
			if (A[i] == A[i + 1]) {
				flag = true;
				break;
			}
		}

		if (flag) {
			System.out.println("NO");
		}
		else {
			System.out.println("YES");
		}
	} main {
		Scanner scanner = new Scanner(System.in);
		int N = scanner.nextInt();
		int[] A = new int[N];
		for (int i = 0; i < N; i++) {
			A[i] = scanner.nextInt();
		}

		Arrays.sort(A);

		boolean flag = false;
		for (int i = 0; i < N - 1; i++) {
			if (A[i] == A[i + 1]) {
				flag = true;
				break;
			}
		}

		if (flag) {
			System.out.println("NO");
		}
		else {
			System.out.println("YES");
		}
	} Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) int N = scanner.nextInt(); N scanner.nextInt() scanner.nextInt scanner int[] A = new int[N]; A new int[N] N for (int i = 0; i < N; i++) {
			A[i] = scanner.nextInt();
		} int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
			A[i] = scanner.nextInt();
		} {
			A[i] = scanner.nextInt();
		} A[i] = scanner.nextInt() A[i] A i scanner.nextInt() scanner.nextInt scanner Arrays.sort(A) Arrays.sort Arrays A boolean flag = false; flag false for (int i = 0; i < N - 1; i++) {
			if (A[i] == A[i + 1]) {
				flag = true;
				break;
			}
		} int i = 0; int i = 0; i 0 i < N - 1 i N - 1 N 1 i++ i++ i {
			if (A[i] == A[i + 1]) {
				flag = true;
				break;
			}
		} {
			if (A[i] == A[i + 1]) {
				flag = true;
				break;
			}
		} if (A[i] == A[i + 1]) {
				flag = true;
				break;
			} A[i] == A[i + 1] A[i] A i A[i + 1] A i + 1 i 1 {
				flag = true;
				break;
			} flag = true flag true break; if (flag) {
			System.out.println("NO");
		}
		else {
			System.out.println("YES");
		} flag {
			System.out.println("NO");
		} System.out.println("NO") System.out.println System.out System System.out "NO" {
			System.out.println("YES");
		} System.out.println("YES") System.out.println System.out System System.out "YES" String[] args args
import java.util.Scanner;
import java.util.Arrays;

class Main {
	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		int N = scanner.nextInt();
		int[] A = new int[N];
		for (int i = 0; i < N; i++) {
			A[i] = scanner.nextInt();
		}

		Arrays.sort(A);

		boolean flag = false;
		for (int i = 0; i < N - 1; i++) {
			if (A[i] == A[i + 1]) {
				flag = true;
				break;
			}
		}

		if (flag) {
			System.out.println("NO");
		}
		else {
			System.out.println("YES");
		}
	}
}