import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		final Scanner scanner = new Scanner(System.in);
		final int counter = scanner.nextInt();
		final int[] array = new int[counter];

		for (int i = 0; i < counter; i++) {
			array[i] = scanner.nextInt();
		}

		int result = 0;
		while (isLoopContinue(array)) {
			boolean bool = false;
			for (int i = 0; i < array.length; i++) {
				if (array[i] > 0) {
					bool = true;
					array[i]--;
				} else {
					if (bool) {
						bool = false;
						result++;
					}
				}
			}
			if (bool) {
				result++;
			}
		}
		System.out.println(result);
		scanner.close();
	}

	public static boolean isLoopContinue(final int[] array) {
		for (int i = 0; i < array.length; i++) {
			if (array[i] > 0) {
				return true;
			}
		}

		return false;
	}

}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz