#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    int N, length[801], rezult = 0, aux;
    freopen("nrtri.in", "rt", stdin);
    freopen("nrtri.out", "wt", stdout);
    cin >> N;

    for(int i = 0; i < N; i++)
        cin >> length[i];

    for(int i = 0; i < N - 1; i++){
        for(int j = i + 1; j < N; j++){
            if(length[i] > length[j]){
                aux = length[i];
                length[i] = length[j];
                length[j] = aux;
            }
        }
    }

    for(int i = 0; i < N - 2; i++)
        for(int j = i + 1; j < N - 1; j++)
            for(int l = j + 1; l < N && length[l] >= length[j] + length[i]; l++)
                rezult++;
    cout << rezult;

    return 0;
}