#include<stdio.h>
#include<math.h>
int main(void)
{
	int n,t,i,sum,xx;
	while(scanf("%d",&n)!=EOF)
	{
		sum=0;xx=0;
		for(i=0;i<n;i++)
		{
			scanf("%d",&t);
			if(t<0)sum=sum+t;else sum=sum+t/2;
			if(sum<0)xx++;
		}
		printf("%d\n",xx);
	}
}