#include <cstdio>
#include <iostream>
#include<algorithm>
#include<cmath>
#include<cstdlib>
#include<cstring>
using namespace std;
int n,m;
int i,j,k;
int main()
{
	while( cin>>n){
		int a,b;
		int sum=0;
		k=0;
		while(n--)
		{

			cin>>a;
			if(a>0)
				a/=2;
			sum+=a;
			if(sum<0)
				k++;
		}
		cout<<k<<endl;
	}
	return 0;
}