#include <iostream>
#include <algorithm>
#include <vector>
#include <iterator>
using namespace std;

int main()
{
	vector<int> stairs;
	copy(istream_iterator<int>(cin), istream_iterator<int>(), back_inserter(stairs));
	int water = 0;
	for (int i = *max_element(stairs.begin(), stairs.end()), S = 0; i >= 0; --i, S = 0)
		for (int j = 0, counter = 0; j < stairs.size(); ++j)
			!S ? S = stairs[j] >= i : (stairs[j] < i ? ++counter : 
				(water += counter, S = counter = 0, j--));
	cout << water << endl;
}