#include <stdio.h>
#include <string.h>
#include <math.h>

int main(){
	int n,death=0,lucky=0,card;
	while(scanf("%d",&n)!=EOF)
	{
		while(n--)
		{
			scanf("%d",&card);
			if(card>0)
				card /= 2;
			lucky += card;
			if(lucky<0)
				death++;
		}
		printf("%d\n",death);
		death=0;
		lucky=0;
	}
}