#include <bits/stdc++.h>
using namespace std;

int main() {
	int n;
	scanf("%d", &n);
	int arr[n];
	for (int i = 0; i < n; i++) {
		scanf("%d", &arr[i]);
	}
	int flag1 = 0;
	int days = 0;
	if (arr[flag1] == 0) {
		flag1++;
	}
	while (arr[flag1] != 0) {
		for (int i = flag1; i < n; i++) {
			if (arr[i] != 0) {
				arr[i]--;
			} else
				break;
		}
		days++;
		for (int i = flag1; i < n;) {
			if (arr[flag1] == 0)
				flag1++;
			else
				break;
		}
		if (flag1 >= n)
			break;
	}
	printf("%d", days);
	return 0;
}