#include<stdio.h>
#include<math.h>
int main(void)
{
	int n,a[1000],i,zf,m;
	while(scanf("%d",&n)!=EOF)
	{
		zf=0;m=0;
		for(i=0;i<n;i++)
		{
			scanf("%d",&a[i]);
			if(a[i]>0)zf=zf+a[i]/2;
			else zf=zf+a[i];
			if(zf<0)m++;
		}
		printf("%d\n",m);
	}
}