JSEPHS: STA  $D0        ; n
        STX  $D1        ; k
        LDA  #$FF
        LDX  #$00
SETUP:  STA  $1000,X    ; populate array with hex FF
        INX
        CPX  $D0
        BEQ  KILL
        JMP  SETUP
KILL:   LDA  #$00       ; number killed so far
        STA  $D2
        LDX  #$00       ; position within array
        LDY  #$01       ; counting up to k
FIND:   INY
SCAN:   INX
        CPX  $D0
        BMI  TEST
        LDX  #$00       ; circle back around
TEST:   LDA  $1000,X
        CMP  #$FF
        BNE  SCAN       ; already been killed
        CPY  $D1
        BMI  FIND       ; if y < k keep going round
        LDA  $D2
        STA  $1000,X    ; mark as dead
        CLC
        ADC  #$01
        STA  $D2
        CMP  $D0        ; have we killed all but 1?
        BPL  RETURN
        LDY  #$00
        JMP  FIND
RETURN: TXA             ; a <- index of survivor
        RTS