Program triunghiuri;

var V : array [1..900] of longint;
    n,i,l,j,m : longint;

procedure swap ( var x,y : longint);
   var aux : longint;
     begin
       aux:=x;
       x:=y;
       y:=aux;

     end;

begin
  assign(input,'nrtri.in'); reset(input);
  assign(output,'nrtri.out'); rewrite(output);
  readln(n); l:=0;
  for i:=1 to n do read(V[i]);

  for i:=1 to n-1 do
    for j:=i+1 to n do
       if V[i]>V[j] then swap(V[i],V[j]);




   for i:=1 to n-2 do
      for j:=i+1 to n-1 do begin
                                 m:=j+1;
                                 while (V[m]<=(V[i]+V[j])) and (m<=n) do begin
                                                                  l:=l+1;
                                                                  m:=m+1;
                                                            end;
                           end;

  writeln(l);


  close(input); close(output);
end.