Var
  n, s, k : longint;
  f, g : text;
  x : double;

Begin
  assign(f, 'input.txt');
  assign(g, 'output.txt');
  reset(f);
  rewrite(g);
  while(not SeekEof(f)) do
    Begin
      s := 0;
      n := 0;
      while(not SeekEoln(f)) do
        Begin
          read(f, k);
          n := n + 1;
          s := s + k;
        End;
      readln(f);
      x := s / n;
      if(not SeekEoln(f)) then write(g, x:0:2, ' ')
        else writeln(g, x:0:2);
    End;
  close(g);
  close(f);
End.