#include<iostream>
#include<algorithm>

using namespace std;

int main(){
	int n,a,c,total;
	while(scanf("%d",&n)!=EOF){
		c=0,total=0;
		while(n--){
			scanf("%d",&a);
			(a>0)?a/=2:0;
			total+=a;
			if(total<0){
				c++;
			}
		}
		printf("%d\n",c);

	}
	return 0;
}