#include <bits/stdc++.h>

using namespace std;

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

int v[801];

int main()
{
    int cnt=0,i,j,k,n;
    in>>n;
    for (i=1;i<=n;i++)
        in>>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[k]<=v[i]+v[j])
                cnt++;
          else
            break;
        }
      }
    }
    out<<cnt;
    return 0;
}