#include<stdio.h>
#include<math.h>
int main(){
int n,sum1,sum2,i;
int a[10001];
while(scanf("%d",&n)!=EOF){
sum1=0;
sum2=0;
for(i=0;i<n;i++){
	scanf("%d",&a[i]);
	if(a[i]>0)
		a[i]=a[i]/2;
	sum1+=a[i];
	if(sum1<0)
		sum2+=1;
}
printf("%d\n",sum2);
}
}