var a:array [1..13] of real;
      i: integer;
      q,s:real;
begin
  s:=3;
  a[1]:=3;
  a[2]:=6;
  a[3]:=12;
  a[4]:=24;
  q:=a[2]/a[1];
  for i:=2 to 13 do
    begin
      a[i]:=a[i-1]*q;
s:=s+a[i];
end;
writeln(s);
end.