#include<fstream>
#include<string.h>
#include<ctype.h>
#include<iostream>
#include<algorithm>
#include<map>
#include<unordered_map>
#include<array>
#include<functional>
#include<deque>
#include<math.h>
#include<unordered_set>
#include<queue>
#include<set>
#include<iomanip>
#include<bitset>
using namespace std;
int n, i, j, x, y, mid, el, sum,l,r;
vector<int>v;
vector<int>::iterator rez;
int main()
{
	//ifstream f("file.in");
	//ofstream g("file.out");
	ifstream f("nrtri.in");
	ofstream g("nrtri.out");
	f >> n;
	for (i = 1; i <= n; i++)
	{
		f >> el;
		v.push_back(el);
	}
	sort(v.begin(), v.end());
	for (i = 0; i < n - 1; i++)
		for (j = i + 1; j < n; j++)
		{
			l = j;
			r = n-1;
			while (l <= r)
			{
				mid = (l + r)/2;
				if (v[mid] <= v[i] + v[j])
					l = mid+1;
				else
					r = mid-1;
			}
			if(r!=j)
				sum += r - j;
		}
	g << sum;
	return 0;
}