#include <fstream>
#include <algorithm>
#define NMAX 800

using namespace std;

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

unsigned short v[NMAX];

int main(){
    ios_base::sync_with_stdio(false);
    fin.tie();
    fout.tie();
    int n, i, j, k, cnt;
    fin >> n;
    for (i = 0; i < n; i++)
        fin >> v[i];
    cnt = 0;
    for (i = 0; i < n - 2; i++)
        for (j = i + 1; j < n - 1; j++)
            for (k = j + 1; k < n; k++)
                if (v[i] <= v[j] + v[k] && v[j] <= v[i] + v[k] && v[k] <= v[i] + v[j])
                    cnt++;
    fout << cnt << '\n';
    return 0;
}