#include<stdio.h>
int main()
{
	int s,n,t,a;
	while(scanf("%d",&n)!=EOF)
	{
		s=0,t=0;
	   while(n--)
	   {
	   	scanf("%d",&a);
	   	s+=a<0?a:a/2;
	   	t+=s<0?1:0;
  
	   }
	   printf("%d\n",t);
    }
}