#include <cstdio>
#include <iostream>
using namespace std;
double m,k,p;
int n;
int main()
{
	while(~scanf("%d",&n)){
		k=0;
		p=0;
		while(n--){
			scanf("%lf",&m);
			if(m>0)
				m=(1.00*m)/2;
			if(k+m<0)
				p+=1;
			k+=m;
		}
		printf("%.0f\n",p);
	}
	return 0;
}