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