start:  STP        ; get input

x:      NOP
y:      NOP

        LDA  x
        SUB  y
        BRZ  start ; x=y, A=0

loop:   LDA  x
        SUB  one
        BRZ  x<y
        STA  x

        LDA  y
        SUB  one
        BRZ  x>y
        STA  y

        JMP  loop

x>y:    LDA  one   ; A := 1
        JMP  start

x<y:    SUB  one   ; A := 0-1
        JMP  start

one:         1