#include <fstream>
#include <algorithm>
#define Nmax 805
using namespace std;

ifstream f("nrtri.in");
ofstream g("nrtri.out");

int sum,a[Nmax],n,i,j,h;

int BinSearch (int val)
{
    int put,poz;
    for (put=1;put<=val;put=put<<1);
    for (poz=1;put;put=put>>1)
     if (a[poz+put]<=val && poz+put<=n)
      poz+=put;
    return poz;
}

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++)
    {
        h=BinSearch(a[i]+a[j]);
        if (a[h]<=a[i]+a[j] && h>j)
         sum+=h-j;
    }
    g<<sum;
    return 0;
}