program ideone;

var
cnt: array[1..26] of integer;
i: integer;
c: char;

begin
    for i := 1 to 26 do
        cnt[i] := 0;

    read(c);

    while c <> '.' do
    begin
        cnt[ord(c) - ord('a')] := cnt[ord(c) - ord('a')] + 1;
        read(c);
    end;

    for c := 'a' to 'z' do
        if cnt[ord(c) - ord('a')] = 1 then
            write(c, ' ');

end.