#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin ("nrtri.in");
ofstream fout ("nrtri.out");
int t[805];
int main()
{
    int i,j,nrnr,counter=0,st,dr,mij,poz;
    fin>>nrnr;
    for(i=1;i<=nrnr;i++)
        fin>>t[i];
    sort(t+1,t+nrnr+1);
    for(i=1;i<=nrnr;i++)
    {
        for(j=i+1;j<=nrnr;j++)
        {
            st=j+1;
            dr=nrnr;
            poz=j;
            while(st<=dr)
            {
                mij=(st+dr)/2;
                if(t[mij]<=t[i]+t[j])
                {
                    poz=mij;
                    st=mij+1;
                }
                else
                {
                    dr=mij-1;
                }
            }
            counter=counter+(poz-j);
        }
    }
    fout<<counter;

    return 0;
}