#include<stdio.h>
#include<math.h>
int main(){
	int n,x,flag;
	double total;
	while(scanf("%d",&n)!=EOF){
		total=0;
		flag=0;
		while(n--){
			scanf("%d",&x);
			if(x>0){
				x=x*0.5;
			}
			total=total+x;
			if(total<0){
				flag=flag+1;
			}
		}
		printf("%d\n",flag);
	}
	return 0;
}