@1
S: MOV UP, ACC
L: MOV ACC, RIGHT
JRO RIGHT

@2
MOV UP, ACC
L: JEZ O
SUB 1
SWP
ADD LEFT
SWP
MOV -1, LEFT
JMP L
O: MOV LEFT, NIL
MOV -2, LEFT
SWP
MOV ACC, DOWN

@5
MOV UP, DOWN

@7
MOV UP, DOWN
