static void Main()
{
var n = int.Parse(Console.ReadLine());
var l = Read();
var set = new IndexedMultiSet <int>();
foreach (var x in l)
{
set.Add(x);
}
Array.Sort(l);
var r = 0;
for (int i = 0; i < n; i++)
{
for (int j = i + 1; j < n; j++)
{
r += set.GetLastIndex(x => x < l[i] + l[j]) - j;
}
}
Console.WriteLine(r);
}
