#include<stdio.h>
int main()
{
	int n,a=0,qz=0;
	float luck=0;
	while(scanf("%d",&n)!=EOF)
	{
		luck=0;
		qz=0;
		while(n--)
		{
			scanf("%d",&a);
			if(a>0&&a%2==1)
			{
				luck=luck+1.0*a/2;
			}
			if(a>0&&a%2==0)
			{
				luck=luck+1.0*a/2;
			}
			if(a<=0)
			{
				luck=luck+a;
			}
			if(luck<0)
			{
				qz++;
			}
		}
		printf("%d\n",qz);
	}
	return 0;
}