#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<math.h>
int main()
{
	double k;
	int n;
	while(scanf("%d",&n)!=EOF)
	{
		double s = 0;
		int p = 0;
		while(n--)
		{
			scanf("%lf",&k);
			if(k > 0)
				s = s + (k/2);
			else
				s = s + k;
			if(s < 0)
				p++;
		}
		printf("%d\n",p);
	}
	
	
	return 0;
}