@1
MOV UP, ACC
MOV ACC, RIGHT
MOV ACC, RIGHT

@2
START: MOV UP, ACC
SAV
NEG
ADD LEFT
JGZ POS
NEG
MOV ACC, DOWN
MOV LEFT, ACC
MOV ACC, DOWN
JMP START
POS: MOV ACC, DOWN
MOV LEFT, NIL
SWP
MOV ACC, DOWN

@5
MOV UP, ACC
SAV
MOV UP, ACC
SWP
L: SUB 2
JLZ DN
SWP
ADD 1
SWP
JMP L
DN: SWP
MOV ACC, DOWN

@9
MOV UP, DOWN
