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