#include<stdio.h>
int main(void){
	int n,a,b,s,i,c;
	while(	scanf("%d",&n) !=EOF){
	s=0,c=0;
	for(i=0;i<n;i++){
		scanf("%d",&a);
		if(a>0)
		a=a/2;
		else a=a;
		b=c+a;
		c=b;
		if(b<0)
		s=s+1;
		else
		s=s;
	}
	printf("%d\n",s);}
	return 0;
}