#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
#include<string>
#include<cmath>
using namespace std;
int main()
{
	double a,b;
	int n;
	while(cin>>n)
	{
		double s=0;
		int sum=0;
		for(int i=0;i<n;++i)
		{
			cin>>a;
			if(a>0) s+=a/2;
			else s+=a;
			if(s<0) sum++;
		}
		printf("%d\n",sum);
	}
}