Program triunghiuri;

var V : array [1..900] of longint;
    b1,b2 :array[0..1 shl 17 ] of char;
    n,i,l,j,m : longint;

begin
  assign(input,'nrtri.in'); settextbuf(input,b1); reset(input);
  assign(output,'nrtri.out'); settextbuf(output,b2); rewrite(output);
  readln(n); l:=0;
  for i:=1 to n do read(V[i]);

  for i:=1 to n-2 do
      for j:=i+1 to n-1 do
                 for m:=j+1 to n do
                        if (V[m]<=V[i]+V[j])
                       and (V[m]+V[i]>=V[j])
                       and (V[m]+V[j]>=V[i]) then l:=l+1;
  writeln(l);
  close(output);
end.