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