Program lol (input, output);
var a, n, b, i, p,s, m:integer;
c:real;
begin
read (n);
a:=n;
b:=0;
c:=0;
I:=0;
p:=1;
while a <> 0 do begin
a:=a div 10;
b:=b+1;
end;
while b <> 0 do
begin
p:=1;
for m:=1 to b do
p:=p*10;
s:=(n mod p) div (p div 10);
if (s mod 2) <> 0 then
begin
c:=c+s;
I:=I+1;
end; b:=b-1;
end;
c:=c/I;
writeln (c);
end.