#include<iostream>
#include<algorithm>
#include<cmath>
#include<cstring>
using namespace std;

int n;
int main() {
	while (scanf("%d", &n) != EOF) {
		int sum = 0;
		int ans = 0;
		int m;
		while (n--) {
			cin >> m;
			if (m > 0)sum += m / 2;
			else sum += m;
			if (sum < 0)ans += 1;
		}
		printf("%d\n", ans);
	}
}