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