#include<stdio.h>
#include<math.h>
int main(){
	double n,m;
	double s=0,t=0;
	while(scanf("%lf",&n)!=EOF){
		while(n--){
			scanf("%lf",&m);
			if(m>0){
				s+=m/2;
			}
			else if(m<0)
			s+=m;
			if(s<0)
			t+=1;
			else
			t+=0;
		}
		printf("%.0lf\n",t);
		s=0,t=0;
	}
}