const NMAX=60;
type realAry=array[1..NMAX]of real;
var v:realAry;
    n,i,binal:integer;
    ans:integer;
procedure sort(s,t);
  var i,j:integer;
      tmp,pivot:real;
begin
  i:=s; j:=t; pivot:=v[(s+t)div 2];
  repeat
    while v[i]<pivot do i:=i+1;
    while v[j]>pivot do j:=j-1;
    if i<=j then begin
      tmp:=v[i]; v[i]:=v[j]; v[j]:=tmp;
      i:=i+1; j:=j-1;
    end;
  until i>j;
  if j>s then sort(s,j);
  if i<t then sort(i,t);
end;

begin
  readln(n);
  for i:=1 to n do read(v[i]);
  sort(1,n);
  ans:=v[1];
  for i:=2 to n do ans:=(ans+v[i])div 2;
  writeln(ans:5:5);
end.