#include<stdio.h>
int main(){
	int n;
	while(scanf("%d",&n)!=EOF){
		int i,a[1000],x,t;
		x=0,t=0;
		for(i=0;i<n;i++){
			scanf("%d",&a[n]);
			if(a[n]>0) a[n]=a[n]/2;
			x=x+a[n];
			if(x<0) t=t+1;
		}
		printf("%d\n",t);
	}
}