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

using namespace std;

ifstream f("nrtri.in");
ofstream g("nrtri.out");

int v[810];

int main()
{
    int n, sol = 0;
    f >> n;
    for(int i = 1; i <= n; i++)
        f >> v[i];
    sort(v + 1,v + n + 1);
    for(int i = 1; i <= n; i++){
        for(int j = i + 1; j <= n; j++){
            for(int k = j + 1; k <= n; k++){
                if(v[k] <= v[i] + v[j])
                    sol++;
                else
                    k = n + 1;
            }
        }
    }
    g << sol;
    return 0;
}