#include <fstream>

using namespace std;

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

int v[805];

int main() {
    int n;
    fin >> n;

    for (int i = 0; i < n; i++) {
        fin >> v[i];
    }

    int cnt_tri = 0;

    for (int i = 0; i < n - 2; i++) {
        for (int j = i + 1; j < n - 1; j++) {
            for (int k = j + 1; k < n; k++) {

                if (v[i] + v[j] >= v[k] &&
                    v[i] + v[k] >= v[j] &&
                    v[j] + v[k] >= v[i])
                    cnt_tri++;

            }
        }
    }

    fout << cnt_tri;


    return 0;
}