var a, b: integer; c, d, e, f: real;
begin
  readln(c);
  d := 0;
  e := c;
  f := c * c;
  for a := 1 to 6 do
  begin
    d := d + e / (2 * a - 1);
    e := e * f;
  end;
  writeln(d:0:4);
end.