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