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