s/^/22/
:L
s/\(.\)\(.\)/\1O\2T/g
s/2./&&/g
s/[12]//g
y/OT/12/
tS
:S
s/\(22112112122121122122121121122121121221221121121221121122121121122122112122121121122122121122122112122121121122121121221121121221211221221121221221121121221121122122121121221121121221221121122121121221121121221221121221211211221221121221211221221211212211211221221\).*/\1/
TL