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

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

    int s=0,i,j,z,n;

    fin>>n;

    int v[n+1];

    for(int i=0;i<n;++i)
    {

        fin>>v[i];

    }
     sort(v,v+n);

    for(i=0;i<n-2;++i)
        {

        for(j=i+1;j<n-1;++j)
            {

            for(z=j+1;z<n;++z){

                if(v[i]+v[j]>=v[z]){

                    ++s;
                }
                else
                    break;
            }
        }
    }

    fout<<s;
}