#include<stdio.h>

int main()
{
	int n,m,x,a;
	while(scanf("%d",&n)!=EOF)
	{
		x=0,a=0;
		while(n--)
		{
			scanf("%d",&m);
			x+=m>0?m/2:m;
			a+=x<0?1:0;
		}
	  printf("%d\n",a);
	}
	return 0;
}