#include<iostream>
#include<string>
#include<cmath>
using namespace std;
int main(){
	int t,a[10000],sum,j;
	while(cin>>t){
		for(int i=0;i<t;++i){
			cin>>a[i];
		}
		sum=0;
		j=0;
		for(int i=0;i<t;++i){
			if(a[i]>0)
			a[i]=a[i]/2;
			sum=sum+a[i];
			if(sum<0)
			j++;
		}
		cout<<j<<endl;
	}
	return 0;
}