/g{dup n le{2 copy add g}if pop dup n le{/n n 2 index sub def/s(1)}{/s(0)}ifelse
s concatstrings def}def/f{(%stdin)(r)file read}def 999{f{dup 49 eq{count 2{1
exch 1 sub{2 mul f pop 2 mod add}repeat}repeat/n exch def/s(1)def 1 2 g s print
clear}{dup 10 eq{pop()=}if}ifelse}if}repeat
Note that non-ascii characters in the above source code will be escaped (such as \x9f).