program Project2;

{$APPTYPE CONSOLE}

uses
  SysUtils;

const
  MAXIN = 100000;

var
  n, i, j: integer;
  a: array [1..MAXIN] of extended;
  x: extended;

begin
  readln(n);

  for i := 1 to n do
    readln(a[i]);


  for i := 2 to n do
    for j := n downto i do
      if (a[j] > a[j - 1]) then
      begin
        x := a[j];
        a[j] := a[j - 1];
        a[j - 1] := x;
      end;

  //for i := 1 to n do
    //writeln(a[i]);

  for i := 1 to n - 1 do
    a[i + 1] := 2 * sqrt(a[i] * a[i + 1]);

  writeln(a[n]:0:2);
  readln;
  readln;
end.