s|$|@ /\\ \n/__\\|
:
/1/{s/1@\| *$//gm;q}
h
s/.@//
s/./a&/gm
:1
s/.*/ & /gm
s/a\(.*\)a/\1/gm
//b1
s/^/%/
H
g
s/.@\|.%.*//g
s/.*/&&/gm
H
x
s/@.*%/@/
y/5432/4321/
b