#include<stdio.h>
int main()
{
	int n,a[1111111],count,i,ans;
	while(scanf("%d",&n)!=EOF)
	{
		ans=0,count=0;
		for(i=0;i<n;++i)
		{
			scanf("%d",&a[i]);
			if(a[i]>0)
			{
				ans+=a[i]/2;
			}
			else
			ans+=a[i];
			if(ans<0)
			count++;
		}
		printf("%d\n",count);
	}
}