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

int main() {
  std::ifstream is{"nrtri.in"};

  int n;
  is >> n;

  std::vector<int> v{n, 0};

  for (auto& i: v)
    is >> i;

  std::sort(begin(v), end(v));

  int s{};

  for (auto i = 0; i < n - 2; ++i)
    for (auto j = i + 1; j < n - 1; ++j)
      for (auto k = j + 1; k < n; ++k)
        if (v[i] + v[j] >= v[k])
          ++s;
        else
          break;

  std::ofstream{"nrtri.out"} << s;
}