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

using namespace std;

int n, i, j, v[800], st, dr, nrt, mid;

int main () {
    
    ifstream fin("nrtri.in");
    ofstream fout("nrtri.out");
    
    fin >> n;
    for (i = 1; i <= n; i++)    fin >> v[i];
    sort (v+1 , v+n+1);
    
    for (i = 1; i <= n-2; i++)
        for (j = i+2; j <= n; j++)
        {
            st = i;     dr = j;
            while (st < dr-1)
            {
                mid = st + (dr-st)/2;
                if (v[mid]+v[st]>=v[dr] && v[mid]+v[dr]>=v[st] && v[st]+v[dr]>=v[mid])
                {   nrt++;   }
                st = mid+1;
            }
        }
    
    fout << nrt << "\n";
}