#include<stdio.h>
#include<math.h>
int main()
{
	int n;
	while(scanf("%d",&n) != EOF)
	{
		int s = 0;
		int k = 0;
		int a[100000];
		for(int i = 0;i < n;i++)
		{
			scanf("%d",&a[i]);
		}
		for(int i = 0;i < n;i++)
		{
			if(a[i] > 0)
				s = s + (a[i] / 2);
			else if(a[i] < 0)
				s = s + a[i];
			if(s < 0)
				k = k + 1;
		}
		printf("%d\n",k);
		
	}
}