#include<stdio.h>
#include<math.h>
int main()
{
	int n,a,k;
	float point;
	while(scanf("%d",&n)!=EOF)
	{
		k=0;
		point=0;
		while(n--)
		{
			scanf("%d",&a);
			if(a>0)
			{
				point+=1.0*a/2;
			}
			else
			{
				point+=a;
			}
			if(point<0)
			{
				k++;
			}
		}
		printf("%d\n",k);
	}
}