#include <iostream>
#include <fstream>
using namespace std;
int main()

{
    int n,i,v[801],j,k,nr=0;
    fstream f("nrtri.in",ios::in);
    fstream g("nrtri.out",ios::out);
    f>>n;
    for(i=1;i<=n;i++)
        f>>v[i];

    for(i=1;i<=n-2;i++)
        for(j=i+1;j<=n-1;j++)
           for(k=j+1;j<=n;j++)
        if((v[i]+v[j]>=v[k]) && (v[i]+v[k]>=v[j]) && (v[k]+v[j]>=v[i]))
        nr++;



    g<<nr;

}