#include<cstdio>
#include<cstring>
#include<cmath>
#include<map>
#include<set>
#include<string>
#include<algorithm>
#define ll long long 
using namespace std;
const int maxn = 200010;
const int inf = 0x3f3f3f3f;
int  x, y, n, k, m;
int main()
{
	while (scanf("%d", &n) != EOF) 
	{
		ll ans = 0;
		m = 0;
		while(n--)
		{
			scanf("%d", &x);
			if (x >= 0)m += (x) / 2;
			else m += x;
			if (m < 0)++ans;
		}
		printf("%d\n", ans);
	}
	return 0;
}