#include<stdio.h>
#include<stdlib.h>
#include<memory.h>
int main()
{
	int n, a[10010], m;
	m = 0;
	int sum1 = 0, sum2 = 0;
	while (scanf("%d", &n) != EOF)
	{
		sum1=0;
		sum2=0;
		memset(a, 0, sizeof(a));
		for (int i = 1; i <= n; i++)
		{
			scanf("%d", &a[i]);
			if (a[i] < 0)
			{
				sum1 += a[i];
			}
			else if(a[i]>0)
			{
				sum1 += a[i] / 2;
			}
			if (sum1 < 0)
				sum2++;
		}
		printf("%d\n", sum2);
	}
	return 0;
}