#include <stdio.h>
#include<math.h>
int main()
{
    int i,n,m,a,dian;
	while(scanf("%d",&n)!=EOF)
	{
		dian = 0;
		m = 0;
		for(i=0;i<n;++i)
		{
			scanf("%d",&a);
			if(a > 0)
			{
				dian += a / 2;
			}
			else
			{
				dian += a;
			}
			if(dian < 0)
			{
				++m;
			}
		}
		printf("%d\n",m);
	}
}