#include<stdio.h>
#include<math.h>
int main()
{
	int n,a,sum;
	double s;
	while(scanf("%d",&n)!=EOF)
	{
	    sum=0;
	    s=0;
		while(n--)
		{
			scanf("%d",&a);
			if(a>0)
			{
				s=s+a*1.0/2;	
			}
			else
			{
				s=s+a;
			}
			if(s<0)
	    	{
	     		sum=sum+1;
	    	}
		}
		printf("%d\n",sum);
	}
}