#include<stdio.h>
int main()
{
	int n,a,x;
	double c;
	while(scanf("%d",&n)!=EOF)
	{
		c=0;x=0;
		while(n--)
		{
			scanf("%d",&a);
			if(a>0)
				c+=a/2.0;
			else
				c+=a;
			if(c<0)
				x++;
		}
	printf("%d\n",x);
	}
	return 0;
}