#include <fstream>
#include <iostream>
#include <algorithm>

using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");

int main()
{
    int n, a[900], sum, cnt = 0;
    fin >> n;
    for (int i = 0; i < n; ++i)
        fin >> a[i];
    sort(a, a + n);

    for (int i = 0; i < n - 1; ++i)
        for (int j = i + 1; j < n; ++j) {
        sum = a[i] + a[j];
        for (int k = j + 1; k < n; ++k)
            if (sum >= a[k])
            ++cnt;
        }
    fout << cnt;
    return 0;
}