#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
long long a[25001],i,j,k,n,nr=0,s;
int main()
{
    f>>n;
    for(i=1;i<=n;i++)
    f>>a[i];
    sort(a+1,a+n+1);

    for (i=1;i<n;i++)
    {
        for (j=i+1;j<=n;j++)
        {
          s=a[i]+a[j];

                for (k=j+1;k<=n;k++)
                if( s>=a[k] )
                 nr++;
        }
    }
    g<<nr;
    return 0;
}