#include <iostream>
#include <fstream>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int i,j,k,nr=0,v[1000],n,ok;
int main()
{
    f>>n;
    for (i=1;i<=n;i++)
    f>>v[i];
    for (i=1;i<=n-2;i++)
        for (j=i+1;j<=n-1;j++)
        {
            ok=1;
            for (k=j+1;k<=n&&ok==1;k++)
            {
                if (v[i]+v[j]>=v[k])
                nr++;
                else ok=0;
            }
        }
    g<<nr;
    return 0;
}