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