#include <iostream>
#include <fstream>
using namespace std;
int N,v[800],i,j,nr;
int main()
{
    ifstream fin;
    fin.open("nrtri.in");
    ofstream fout;
    fout.open("nrtri.out");
    fin>>N;
    nr=0;
    for(i=1;i<=N;i++)
        fin>>v[i];
    for(i=1;i<N-1;i++)
    {
        for(j=i+1;j<N;j++)
        {
            for(int q=j+1;q<=N;q++)
            {
                if((v[i]+v[j]>=v[q])&&(v[i]+v[q]>=v[j])&&(v[q]+v[j]>=v[i]))
                    nr=nr+1;
            }
        }
    }
    fout<<nr;
    fout.close();
    return 0;
}