#include<iostream>
#include<fstream>
using namespace std;

int main()
{
    ifstream cin("nrtri.in");
    ofstream cout("nrtri.out");
    int n,k,a,b,c,v[801];
    k=0;
    cin>>n;

    for(i=1;i<=n;i++)
    {
        cin>>v[i];
    }

    for(a=1;a<=n-2;a++)
    {
           for(b=a+1;b<=n-1;b++)
           {
                    for(c=b+1;c<=n;c++)
                    {
                             if(v[a]+v[b]>=v[c] && v[b]+v[c]>=v[a] && v[a]+v[c]>=v[b])
                             {
                               k++;
                             }
                    }
           }
    }
    cout<<k;


}