#include <fstream>
#include <algorithm>
using namespace std;
ifstream in ("nrtri.in");
ofstream out ("nrtri.out");
int v[100001], n, i, t, j, s;

int main()
{
    int n, i;
    in >> n;
    for(i=1; i<=n; i++)
    {
        in >> v[i];
    }
    sort (v+1, v+n+1);
    for(i=2; i<n; i++)
    {
        j=1;
        t=i+1;
        while(j<i)
        {
            while(t<n && v[i]+v[j]>=v[t])
            {
                    s++;
                    t++;
            }
            j++;
            s++;
        }
    }
    out << s;
    return 0;
}