#include <fstream>
#include <algorithm>
using namespace std;

ifstream f("nrtri.in");
ofstream g("nrtri.out");

int n, v[801];
int cautbin(int a, int b)
{
    int r = 0;
    int pas = 1 << 16;
    while (pas)
    {
        if (r + pas < n && v[r + pas] <= a + b)
            r += pas;
        pas /= 2;
    }
    return r;
}
int main()
{
    int i, k, tri = 0, j;
    f >> n;
    for (i = 0; i < n; i++)
        f >> v[i];
    sort (v, v + n);
    for (i = 0; i < n - 1; i++)
    {
        for (j = i + 1; j < n; j++)
            tri += cautbin(v[i], v[j]) - j;
    }
    g << tri;
    return 0;
}