#include<stdio.h>
int main()
{
	int n;
	while(scanf("%d",&n)!=EOF)
	{
		int t=0;
		double k=0;
		for(int i=0;i<n;i++)
		{
			int y;
			scanf("%d",&y);
			if(y>0)
			k+=y/2.0;
			else if(y<0)
			k+=y;
			if(k<0)
			t++;
		}
		printf("%d\n",t);
	}
	return 0;
}