/**
 * @brief https://www.infoarena.ro/problema/nrtri
 */
#include <bits/stdc++.h>
using namespace std;
ifstream in("nrtri.in");
ofstream out("nrtri.out");
const int NMAX = 800;


int main()
{
    int v[NMAX], n, sum=0;
    in >> n; 
    for(int i = 0; i < n ;i ++){ 
        in >> v[i];
    }
    sort(v, v + n);
    for(int i = 0 ; i < n -2; i ++){ 
        for(int j = i+1; j < n-1; j ++){ 
            int val = v[i] + v[j] + 1;
            int poz = lower_bound(v + j + 1, v + n, val) - v;
            int nr_triunghiuri = poz - j - 1;
            sum += nr_triunghiuri;
        }
    }
    out << sum;

    return 0;
}