#include <iostream>
#include <fstream>
#include <cmath>

using namespace std;

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

int main(){
    int n;
    fin >> n;
    int v[n];
    for(int i=0;i<n;i++)
        fin >> v[i];
    int i,j,k;
    int rasp=0;
    for (i=0;i<n;i++)
        for (j=i+1;j<n;j++)
            for(k=j+1;k<n;k++) {
                int s_ij=v[i]+v[j];
                int s_ik=v[i]+v[k];
                int s_jk=v[j]+v[k];
                if(s_ij>=v[k] && s_ik>=v[j] && s_jk>=v[i])
                    rasp++;
            }
    fout << rasp;
}