#include<bits/stdc++.h>
using namespace std;
int main (){
	int n,s,a,sum;
	while(cin>>n){
		sum=0;
		s=0;
		for(int i=0;i<n;++i){
			cin>>a;
			if(a>0)
			a/=2;
			s+=a;
			if(s<0)
			++sum;
		}
		cout<<sum<<endl;
	}
	return 0;
}