#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");

int n, s, x, rez;
vector<int> v;

int main()
{
    int i;
    vector<int>::iterator it, jt, kt;
    f>>n;
    for (i = 1;i <= n;i++)
    {
        f>>x;
        v.push_back(x);
    }
    for (it = v.begin();(it + 2) != v.end();it++)
        for (jt = it + 1;(jt + 1) != v.end();jt++)
        {
            s = *it + *jt;
            for (kt = jt + 1;kt != v.end() && *kt <= s;kt++)
                if (*it + *kt >= *jt && *jt + *kt >= *it)
                    rez++;
        }
    g<<rez;
}