#include<cstdio>
#include <algorithm>
#include <iostream>
#include<cstring>
#include<cmath>
using namespace std;
const int maxn=110;
int main()
{
	int n,i,a,ans,sum;
		while(~scanf("%d",&n))
		{
			sum=0;ans=0;
			for(i=1;i<=n;i++)
			{
			scanf("%d",&a);
			if(a>0){a=a/2;}
			sum+=a;
			if(sum<0){ans++;}
			}
			printf("%d\n",ans);
		}
//	system("pause");
}