Var
     t_days: array[1..7] of real;
     s_a: real;
     i: integer;
Begin
  for i:= 1 to 7 do
   read (t_days[i]);
  for i:= 1 to 7 do
   s_a:= t_days [i] + s_a;
  s_a:= s_a / 7;
  writeln (s_a: 5: 2);
End.