Program Pku_1004;
Var s , m : Double;
q  : Integer;
 
Begin
s := 0.0;q := 0;
While q < 12 Do
  Begin
    Readln(m);
    s := s + m;
    q := q + 1;
  End;
s := s / 12;
Writeln('$',s:0:2);
readln
end.