#include<stdio.h>
#include<math.h>
#include<string.h>
int main(){
	int n,m,k,t,i,j;
	int a[10000];
	while(scanf("%d",&n)!=EOF){
	for(i=0;i<n;i++){
		scanf("%d",&a[i]);
	}
	k=0;t=0;
	for(i=0;i<n;i++){
		if(a[i]>0)
			a[i]=a[i]/2;
		{k+=a[i];}
		if(k<0)
		{t+=1;}
	}
	printf("%d\n",t);
	}
	return 0;
}