#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

int triunghi(int a, int b, int c)
{
    if(a <= b + c && b <= a + c && c <= a + b)
        return 1;
    return 0;
}

int main()
{
    ifstream in("nrtri.in");
    int n;
    in >> n;
    vector <int> v;
    for(int i = 1; i <= n; i++)
    {
        int t;
        in >> t;
        v.push_back(t);
    }
    in.close();
    sort(v.begin(), v.end());
    int nrtri = 0;
    for(int i = 0; i < n - 2; i++)
        for(int j = i + 1; j < n - 1; j++)
        {
            int k = j + 1;
            while(triunghi(v[i], v[j], v[k]) && k < n)
                nrtri++, k++;
        }
    ofstream out("nrtri.out");
    out << nrtri;
    out.close();
}