#include <fstream>

#include <algorithm>

using namespace std;

int n,i,v[810],j,p,u,m,s,k,ap;

ifstream fin ("nrtri.in");

ofstream fout ("nrtri.out");

int main (){

    fin>>n;
    for (i=1;i<=n;i++)
        fin>>v[i];
    sort (v+1, v+n+1);
    for (i=1;i<=n-2;i++)
        for (j=i+1;j<=n-1;j++){
            s = v[i] + v[j];

            for (k=j+1;k<=n;k++)
                if (v[i]+v[j] >= v[k])
                    ap++;
                else
                    break;
        }
    fout<<ap;

    return 0;
}