ใใใช็ต้จใใชใใจใใไบบใใใใใ ใใใฏๅคงๅคใใใใพใใใใจใงใ ใงใใชใใ ใใ ใใใใไบบใฎๆนใๅคใใใใใชใใใชใฃใฆ ๆใใ
ๆจๆฅใใใใๅใฃใฆใ ไปฒ่ฏใใชใฃใฆใ ใใฃใใๅ้ใ ใจๆใฃใฆใใฎใซใ ไปๆฅไผใฃใใใใใณใใ่ฉฑใใฆใใใชใใฆใ ๆจๆถใใฆใใใชใใฆใ ๅใฏๅฟ ๆญปใซไผ้ใใใใใใฎใซใ ใใใซใ่ฟใใฆใใใชใใ
ไบบ้ใฏๆฐใพใใใ ใใใ
ใ็ซใฏๆฐใพใใใใ ใจๆๅณใ้ๅ้ใใญใ
็ตถๅฏพๆ่ชญใใ ใใจใฎใใๆฌใซๆธใใฆใใฃใใฏใใชใฎใซใ ไฝใ่ฆใใฆใชใใ ่ชญใฟๆนใๆชใใฎใ ใใใใ ใงใใๅคงไบใใใชใจใใใ ใๆพใ่ชญใฟใใฆใ ็ตๆไฝใๆฎใใชใใใใช่ชญใฟๆนใฏ็ใงๆฒปใใชใใ ใใใ
stack = []
has_read (book) ->
stack.push book if valuable book
rec = ->
book = stack.shift()
begin_read book, ->
has_read book
do rec
do rec