#include <fstream>
#include <algorithm>

using namespace std;

ifstream f("nrtri.in");
ofstream g("nrtri.out");
int v[805];
int n;

int cb(int x)
{
    int st = 1;
    int dr = n;
    int poz = -1;
    int m;

    while(st <= dr)
    {
        m = (st + dr) / 2;
        if(v[m] <= x)
        {
            poz = m;
            st = m+1;
        }
        else
        {
            dr = m - 1;
        }
    }
    return poz;
}

int main()
{
    f>>n;
    for(int i = 1; i<=n; i++)
    {
        f>>v[i];
    }

    sort(v+1, v+n+1);

    int ans = 0;

    for(int i = 1; i<=n-2; i++)
    {
        for(int j = i+1; j<=n-1; j++)
        {
            ans += max(0, cb(v[i]+v[j])-j);
        }
    }

    g<<ans;
    return 0;
}