#include<stdio.h>
int main()
{
	int n,a[100000],b=0,i,j;
	double sum=0;
	while(scanf("%d",&n)!=EOF)
	{
		b=0,sum=0;
		for(i=0;i<n;i++)
		{
			scanf("%d",&a[i]);
		}
		for(j=0;j<n;j++)
		{
			if(a[j]>0)
			{
				sum+=(double)a[j]/2;
			}
			else
				sum+=a[j];
			if(sum<0)
				b++;
		}
		printf("%d\n",b);

	}
	return 0;
}