const
  N = 5;

var
  a: array[1..N] of integer;
  i, x, y: integer;
  s: real;

begin
  for i := 1 to N do
    readln(a[i]);
  x := 0; //sum
  y := 0; //k
  for i := 1 to N do
    if (a[i] > 20 ) then
    begin
      x := x + a[i];
      y := y + 1;
    end;
  s := x / y;
  writeln(s);
end.