两篇题解全被 hack 了（如果是我题意理解错误，可重喷）

input

"bybyby" by byby
"by ppp" by liangruichen
"by sbsb" by Lh AK IOI
END
BORROW "bybyby"
BORROW "by ppp"
RETURN "bybyby"
RETURN "by ppp"
SHELVE
END

output

Put "bybyby" after "by sbsb"
Put "by ppp" after "bybyby"
END