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