#include<stdio.h>
#include<math.h>
#include<string.h>
#include<algorithm>
int main()
{
	int n;
	while(scanf("%d",&n)!=EOF)
	{
		int a[100010];
		int i,s=0;
		double num=0;
		for(i=0;i<n;i++)
		{
			scanf("%d",&a[i]);
		    if(a[i]>0)
			{
				num+=double(a[i])/2;
			}
			else
				num+=a[i];
			if(num<0)
			{
				s+=1;
			}
		}
		printf("%d\n",s);
	}



}