import java.util.Scanner;

public class Main {

	private static int[] minSegment;

	private static int n;

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);

		int n = sc.nextInt();
		int[] hList = new int[n];
		for(int i = 0; i < n; i++) {
			hList[i] = sc.nextInt();
		}

		int count = 0;
		boolean allzero = false;

		while(!allzero) {
			allzero = true;
			boolean zeroFlg = true;
			for(int i = 0; i < n; i++) {
				int h = hList[i];

				if(h > 0) {
					if(zeroFlg) {
						count++;
					}
					hList[i] = h-1;
					zeroFlg = false;
					allzero = false;
				} else {
					zeroFlg = true;
				}
			}

		}


		System.out.println(count);

	}

}


/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