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