#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;i++)
    {
        for(j=i+2;j<=N;j++)
        {
            if((v[i]+v[i+1]>=v[j])&&(v[i]+v[j]>=v[i+1])&&(v[i+1]+v[j]>=v[i]))
                nr=nr+1;
        }
    }
    fout<<nr;
    fout.close();
    return 0;
}