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