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

int n, i, v[805], j, st, dr, mij, nrtri;

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

int main()
{
        fin>>n;
        for(i=1; i<=n; i++)

    {
                fin>>v[i];

    }
        sort(v+1, v+n+1);
        for(i=1; i<n-1; i++)
    {
                for(j=i+1; j<n; j++)
        {
                        st = j+1;
                        dr = n;
                        while(st <= dr)
            {
                                mij = (st+dr)/2;
                                if(v[mij] <= v[i]+v[j])
                {
                                        st = mij+1;

                }
                else
                {
                                        dr = mij-1;

                }

            }
                        nrtri += dr-j;

        }

    }
        fout<<nrtri;
}