#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream fi("nrtri.in");
ofstream fo("nrtri.out");

int v[800];

int main()
{
  long long n, i, j, pas, rez, rasp;
  fi >> n;
  for(i = 0; i < n; i++)
    fi >> v[i];
  sort(v, v + n);
  rasp = 0;
  for(i = 0; i < n; i++)
    for(j = i + 1; j < n; j++){
      rez = 0;
      for(pas = 1 << 10; pas > 0; pas /= 2)
        if(rez + pas < n && v[rez + pas] <= v[i] + v[j])
          rez += pas;
      rasp += rez - j;
    }
  fo << rasp;
  return 0;
}