#include<string>
#include <iostream>
using namespace std;


int main() {

	int prev, succ, n, a[1000], s, c,g, result=0;
	cin >> n;
	a[0] = 0;
	for (int i = 1; i < n; i++) {
		cin >> a[i];
	}
	for (int i = 1; i < n; i++) {
		if (a[i] < 0) {
			s = a[i - 1] + a[i];
			if (s < 0) {
				g = abs(a[i]);
				result++;
				c = result + a[i];
				if (c == 0) {
					result++;
				}

			}
		}
	}
	result--;
	cout << result;


}