uses crt;
var
s,ch:string;
i,error:integer;
function chislo(a:char):string;
begin
if (a='0') or
(a='1') or
(a='2') or
(a='3') or
(a='4') or
(a='5') or
(a='6') or
(a='7') or
(a='8') or
(a='9') then
chislo:=a
else
chislo:='';
end;
begin
readln(s);
ch:='';
for i:=1 to length(s) do
ch:=ch+chislo(s[i]);
val(ch,i,error);
writeln(sqrt(i):4:1);
readln;
end.