n       equ 8 ; queens
maximum equ 32 ; only limited by time
place   equ $00
count   equ maximum+place ; 64 bits (8 bytes)
length  equ maximum+8
        org $80
start
	LDY #n ; n queens on an n x n board
	STY  greater+1
	DEY
	STY  safe+1
	LDX #length
	LDA #$00
clear
	STA  place,X
	DEX
	BPL  clear
next
	INX
	LDA #$FF
	STA  place,X
loop
	INC  place,X
	LDA  place,X
greater
	CMP #n
	BCS  max
	STX  index+1
index
	LDY #$00 ; index+1
	BEQ  safe
	DEY
	STA  compare+1
	STA  add+1 ; compare
	STA  sub+1 ; compare
issafe
	LDA  place,Y
compare
	CMP #$00 ; compare+1
	BEQ  loop ; unsafe
	INC  add+1
add
	CMP #$00 ; add+1
	BEQ  loop ; unsafe
	DEC  sub+1
sub
	CMP #$00 ; sub+1
	BEQ  loop ; unsafe
	DEY
	BPL  issafe
safe
	CPX #n-1
	BNE  next
	INC  count ; 64 bits (8 bytes)
	BNE  loop
	INC  count+1
	BNE  loop
	INC  count+2
	BNE  loop
	INC  count+3
	BNE  loop
	INC  count+4
	BNE  loop
	INC  count+5
	BNE  loop
	INC  count+6
	BNE  loop
	INC  count+7
	BNE  loop
	BRK
max
	DEX
	BPL  loop
;	RTS