#include <stdio.h>

int main() {
	int n,sum,a,ans;
	while(scanf("%d",&n)!=EOF)
	{
		sum=0,ans=0;
		while(n--)
	{
		scanf("%d",&a);
		if(a>0){
			a/=2;
			sum+=a;
		}
		else
		{
			sum+=a;
		}
		if(sum<0)
			ans+=1;
	}
	printf("%d\n",ans);
	}
	return 0;
}