program textcuv;
 const
      alfabet=['a'..'z','A'..'Z'];
 var
    f:text;
    ch:char;
    c,l:longint;
     r:real;
begin
 assign(f,'text.in');
 reset(f);
  read(f,ch);
   while not eoln(f) do
    begin
     while not (ch in alfabet) do
      read(f,ch);
       if not eoln(f) then
        inc(c);
       while ch in alfabet do
        begin
         read(f,ch);
         inc(l);
        end;
    end;
     close(f);
 assign(f,'text.out');
 rewrite(f);
  r:=l/c;
  write(f,r);
 close(f);
end.