Function A($)	
	$a = $^0
	dim $i, $x, $b,$s

		for $i = -$a to -1
			$x = substr($,-$i,1)
			$b = $b+'+'+($s*((4<$x)+$x)+$x)
			$s=$s^1
		next

		$i = execute("$X="+$b)
		$a = ($>3 & $<7 & $a=16-($<4) & $x mod 10=)*left($,1)
Endfunction

Function A($)	
	$a = $^0
	dim $i, $x, $b,$s

		for $i = -$a to -1
			$x = substr($,-$i,1)
			$b = $b+$s*((4<$x)+$x)+$x
			$s=$s^1
		next
		$a = ($>3 & $<7 & $a=16-($<4) & $b mod 10=)*left($,1)
Endfunction