#include <algorithm>
#include <fstream>
#include <iostream>
using namespace std;

const int MAX_N = 805;

int a[MAX_N];

int UpperBound(int left,int right,int x) {
    int best = 0;
    while (left <= right) {
        int middle = (left + right) / 2;
        if (a[middle] <= x) {
            best = middle;
            left = middle + 1;
        } else {
            right = middle - 1;
        }
    }
    return best;
}

int main() {
    ifstream cin("nrtri.in");
    ofstream cout("nrtri.out");
    int n;
    cin >> n;
    for (int i = 1; i <= n; ++ i) {
        cin >> a[i];
    }
    sort(a + 1, a + n + 1);
    int total = 0;
    for(int i = 1; i <= n; ++ i) {
        for(int j = i + 1; j <= n; ++ j) {
            int k = UpperBound(j + 1, n, a[i] + a[j]);
            if (k) {
                total += k - j;
            }
        }
    }
    cout << total << "\n";
    return 0;
}