#include<stdio.h>
int main()
{
	int i,j,n,m,k,a=0,b=0;
	while(scanf("%d",&n)!=EOF)
	{
	for(i=0;i<n;i++)
	{
		scanf("%d",&m);
		if(m>0)a=a+m*1.0/2;
		else a=a+m;
	    if(a<0)b=b+1;
	}
	printf("%d\n",b);
	a=0,b=0;
	}
}