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