#include <fstream>
#include <algorithm>
using namespace std;
int v[801];
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int main()
{
    int n,i,j,k,solutie=0;
    f >>n;
    for (i=1;i<=n;i++)
        f >>v[i];
    sort (v+1,v+n+1);
    for (i=1;i<=n-2;i++)
        for (j=i+1;j<=n-1;j++)
            for (k=j+1;k<=n;k++)
            {
                if (v[i]+v[j]>=v[k])
                    solutie++;
            }
    g <<solutie;
    return 0;
}