#include<cstdio>
#include<cmath>
#include<cstring>
#include<algorithm>
using namespace std;
int main()
{
	double n,a,b;
	int s;
	while(~scanf("%lf",&n))
	{   
		s=0,b=0;
		while(n--)
		{
		scanf("%lf",&a);
		if(a>0)
		 b=b+a/2;
		if(a<=0)
		  b=b+a;
		if(b<0)
		  s=s+1;
		}
		printf("%d\n",s);
	}
}