#include<stdio.h>
int main()
{
	int n;
	while(scanf("%d",&n)!=EOF)
	{
		int a,sum;
		double b;
		sum=0,b=0.0;
		while(n--)
		{
			scanf("%d",&a);
			if(a<0)
			{
				b+=a*1.0;
			}
			else
				b=b+a*1.0/2;
			if(b<0)
				sum+=1;
		}
		printf("%d\n",sum);
		sum=0;
	}
}