#include<iostream>
#include<cmath>
#include<cstring>
#include<stack>
#include<set>
#include<algorithm>
#include<map>
#include<cstdlib>
using namespace std;
int main()
{
	int n;
	while(scanf("%d",&n)!=EOF)
	{
		int ans=0;
		int sum=0;
		while(n--)
		{
			int b;
			scanf("%d",&b);
			if(b>=0)
			sum+=b/2;
			if(b<0)
			sum+=b;
			if(sum<0)
			ans++;
		}
		printf("%d\n",ans);
	}
}