program abc(input,output);
var a:integer;
    b:real;
  function fuc(x:integer):real;
  begin
    if(x<=2)
      then
        begin
          if (x=1) then fuc:=2 else fuc:=4;
        end
      else
        fuc:=fuc(x-1)*fuc(x-2)/2;
  end;
begin
  a:=7;
  b:=fuc(a);
  writeln(b:5:0);
end.