#include<stdio.h>
#include<stdlib.h>
#include<memory.h>
int main()
{
	int n,a[10010],m;
	m=0;
	int sum1=0,sum2=0;
	while(scanf("%d",&n)!=EOF)
	{
		sum1=0;
		sum2=0;
		memset(a,0,sizeof(a));
		for(int i=1;i<=n;i++)
		{
			scanf("%d",&a[i]);
			if(a[i]<0)
			{
				sum1+=a[i];
			}
			else if(a[i]>0)
			{
				sum1+=a[i]/2;
			}
			if(sum1<0)
			{
				sum2++;
			}
		}
		printf("%d\n",sum2);
	}
}