#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

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


int main()
{
    vector<int> val;
    int n, x;
    long long ct = 0;
    fin >> n;
    for(int i = 0; i < n; i++){
        fin >> x;
        val.push_back(x);
    }

    sort(val.begin(), val.end());

    for(int i = 0; i < n-2; i++){
        for(int j = i+1; j < n-1; j++){
            int left = j + 1, right = n - 1, best_k = j;
            int k = j + 1;
            while (k < n && val[i] + val[j] >= val[k]) {
                ct++;
                k++;
            }
        }
    }
    fout << ct;
    return 0;
}