#include<stdio.h>

int main()
{
	int n,a,q = 0,z = 0;
	while(scanf("%d",&n) != EOF)
	{
	while(n--)
	{
		scanf("%d",&a);
		if(a > 0)
		q = q + a / 2;
		else
		q += a; 
		if(q < 0)
		z++;
	}
	printf("%d\n",z);
	z = 0;
	q = 0;
}
	return 0;
}