#include <iostream>
#include <vector>
#include <fstream>

using namespace std;
int n,i,j,t,c,x;
vector<int>v;

int main()
{
    ifstream fin("nrtri.in");
    ofstream fout("nrtri.out");
    fin>>n;
    for (i=0;i<n;i++)
    {
        fin>>x;
        v.push_back(x);
    }
    for (i=0;i<v.size()-2;i++) for (j=i+1;j<v.size()-1;j++) for (t=j+1;t<v.size();t++)
    {
        if (v[i]+v[j]>=v[t] and v[i]+v[t]>=v[j] and v[t]+v[j]>=v[i])
        {
            c++;
        }
    }
    fout<<c;
}