#include<stdio.h>
int main(void){
int a,n,luck=0,total=0;
while(scanf("%d",&n)!=EOF){
	while(n--){
	  scanf("%d",&a);
	  if(a>0) a=a/2;
	  luck=luck+a;
	  if(luck<0) total=total+1;
	}
	printf("%d\n",total);
	total=0;
	luck=0;
}

}