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