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

using namespace std;

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

int v[803];

int main() {

    int n;
    in >> n;

    for(int i = 0; i < n; i++)
        in >> v[i];

    sort(v, v+n);

    int am = 0;

    for(int i = 0; i < n; i++) {
        for(int j = i+1; j < n; j++) {
            int uw = upper_bound(v, v+n, v[i]+v[j]) - v;
            /*int a = j+1;
            while(a < n && v[a] <= v[i]+v[j])
                a++;*/
            am += uw-j-1;
        }

    }

    out << am;

    return 0;
}