#include <fstream>
#include <algorithm>

using namespace std;

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

const int N = 802;

int n, v[N], s;

void cautbin(int i, int j) {
    int r = 0, pas = 1 << 15, lung = v[i] + v[j];
    while (pas != 0) {
        if (r + pas <= n && v[r + pas] <= lung) {
            r += pas;
        }
        pas >>= 1;
    }
    s += r - j;
}

int main()
{
    in >> n;
    for (int i = 1; i <= n; i++) in >> v[i];
    sort(v + 1, v + n + 1);

    for (int i = 1; i <= n; i++) {
        for (int j = i + 1; j <= n; j++) {
            cautbin(i, j);
        }
    }
    out << s;
}