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

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

int n, a[802];

int caut(int s, int st1, int dr1)
{
    int st, dr;
    st = st1;
    dr = dr1;
    int maxim = 0;
    while(st <= dr)
    {
        int m = (st + dr) / 2;
        if (a[m] <= s)
        {
            maxim = m;
            st = m + 1;
        }
        else
        {
            dr = m - 1;
        }
    }
    return maxim;
}

int main()
{
    cin >> n;
    for(int i = 1;i <= n; ++i)
    {
        cin >> a[i];
    }
    int c = 0;
    sort(a + 1, a + n + 1);
    for(int i = 1; i <= n; ++i)
    {
        for(int j = i + 1; j <= n; ++j)
        {
            int s = a[i] + a[j];
            int k = caut(s, j + 1, n);
            if(k != 0)
            {
                c = c + (k - j);
            }
        }
    }
    cout << c << '\n';
    return 0;
}