#include<stdio.h>
int main ()
{
	int i,n,a[10000],sum1,sum2;
	while(scanf("%d",&n)!=EOF)
	{
		sum1=sum2=0;
		for(i=0;i<n;++i)
		{
			scanf("%d",&a[i]);
		}
		for(i=0;i<n;++i)
		{
			if(a[i]>0)
			{
				sum1=sum1+a[i]/2;
			}
			else
			{
				sum1=sum1+a[i];
			}
			if(sum1<0)
		    {
	  	    	sum2=sum2+1;
	    	}
		}
		printf("%d\n",sum2);
	}
	return 0;
}