#include <iostream>
#include <fstream>
#include <algorithm>

using namespace std;

ifstream fin("nrtri.in");
ofstream fout("nrtri.out");

int vect[801], n;

/*void afiseaza(){
    for(int i = 0; i < n; i++){
        cout << vect[i] << " ";
    }
    cout << endl;
}*/

int main()
{
    int i, numarDeTriunghiuriPosibile = 0, z, j;
    fin >> n;
    for(i = 0; i < n; i++){
        fin >> vect[i];
    }
    sort(vect, vect + n);
    for(i = 0; i < n - 2; i++){
        for(j = i + 1; j < n - 1; j++){
            for(z = j + 1; z < n; z++){
                if(vect[i] + vect[j] >= vect[z]){
                    numarDeTriunghiuriPosibile++;
                }
            }
        }
    }
    fout << numarDeTriunghiuriPosibile;
    return 0;
}