
const NMAX=100010;
type intary =array[1..NMAX]of integer;
var n,i,j,k:integer;
    ans:real;
    a:intary;

procedure sort(p,q:integer;var s:array[1..NMAX]);
  var i,j,k,w:integer;
begin i:=p;j:=q; k:=s[(p+q) div 2];
  repeat
    while s[i]<k do i:=i+1;
    while k<s[j] do j:=j-1;
    if i<=j then begin
      w:=s[i]; s[i]:=s[j]; s[j]:=w;
      i:=i+1; j:=j-1
    end
  until i>j;
  if p<j then sort(p,j);
  if i<q then sort(i,q)
end;

begin
  readln(n);
  for i:=1 to n do read(a[i]);
  sort(1,n,a);
  j:=0; k:=1;
  for i:=1 to n do 
  begin
    j:=j+a[i]*k;
    if i<>n then k:=k<<1;
  end;
  ans:=j/k;
  writeln(ans);
end.
