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

ifstream fin; ofstream fout;
int a[810],i,j,k,n; long N;

int main () {
    fin.open ("nrtri.in"); fout.open ("nrtri.out");
    fin>>n;
    for (i=0; i<n; i++) fin>>a[i];
    sort (a,a+n);
    for (i=0; i<n-2; i++)
        for (j=i+1; j<n-1; j++)
            for (k=j+1; (a[i]+a[j]>=a[k])&&(k<n); k++)
                N++;
    fout<<N<<endl;
    fin.close (); fout.close ();
    return 0;
}