#include<iostream>
#include<iomanip>
#include<algorithm>
#include<cmath>
#include<string>
using namespace std;
int main(){
	/*int T,a,Ta,b,Tb,tm,ts;
	char s;
	cin>>T;
	while(T--){
		cin>>a>>Ta>>b>>Tb>>tm>>s>>ts;
	}
	*/
	int n,x,sum=0,qiu=0;
	while(cin>>n){
		sum=0;
		qiu=0;
		for(int i=0;i<n;i++){
			cin>>x;
			if(x>0)			sum=sum+x/2;
			else 			sum=sum+x;
			if(sum<0)	qiu++;
		}
		cout<<qiu<<endl;
	}
	//system("pause");
	return 0;
}