Pascal :

program calfflac;
var
  s:array[1..20000]of char;
  lch,max,i,first,last:integer;
procedure check(odd:byte);
var
  lth,l,r,b,e:integer;
begin
  l:=i; r:=i+odd;
  if odd=1 then
    begin
      while (r<=lch)and(not(s[r] in ['a'..'z','A'..'Z'])) do inc(r);
      if (r>lch)or(upcase(s[r])<>upcase(s[l])) then exit;
      lth:=0;
    end
  else lth:=-1;
  repeat
    b:=l; e:=r;
    inc(lth,2); dec(l); inc(r);
    while (1<=l) and (not (s[l] in ['a'..'z','A'..'Z'])) do dec(l);
    while (r<=lch) and (not (s[r] in ['a'..'z','A'..'Z'])) do inc(r)
  until (l<1) or (r>lch) or (upcase(s[l])<>upcase(s[r]));
  if lth>max then
    begin
      first:=b;
      last:=e;
      max:=lth;
    end;
end;
begin
  lch:=0;
  while not eof do
    begin
      inc(lch); read(s[lch]);
    end;
  max:=1; first:=1; last:=1;
  for i:=1 to lch do
    begin
      if not(s[i] in ['a'..'z','A'..'Z']) then continue;
      check(0); check(1);
    end;
  writeln(max);
  for i:=first to last do write(s[i]);
  writeln;
end.