Program triunghiuri;

var V : array [1..900] of longint;
    n,i,l,j,k,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:=i+2;
           while V[m]< V[i]+V[j] do begin
                                          l:=l+1;
                                          m:=m+1;
                                    end;
                                  end;


  writeln(l);


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