var a:array [1..800] of integer;
    i, n, j, l, k:integer;
    f, g:text;
begin assign(f, 'nrtri.in');
      assign(g, 'nrtri.out');
      reset(f); rewrite(g);
      readln(f, n);
      k:=0;
      For i:=1 to n do read(f, a[i]);
      For i:=1 to n-2 do
         For j:=i+1 to n-1 do
            For l:=j+1 to n do
               if (a[i]+a[j]>=a[l]) and (a[j]+a[l]>=a[i]) and (a[l]+a[i]>=a[j]) then k:=k+1;
      write(g, k);
      close(f); close(g);
end.