#include<stdio.h>
#include<math.h>
#include<string.h>
#include<stdlib.h>
int main()
{
	int n,a,count;
	double s;
	while(scanf("%d",&n)!=EOF)
	{
		s=0;count=0;
		while(n--)
		{
			scanf("%d",&a);
			if(a>0)
			{
				s+=a/2.0;
			}
			else
			{
			    s+=a;
			}
			if(s<0)
		    { 
			  count++;
		    }	
		}
		
		printf("%d\n",count);
	}
	return 0;
}