use 5.014; use warnings;
our($R, $C, $M) = (14, 14, 7);
if (@ARGV) {
	3 == @ARGV or die "Usage: lights R C M";
	($R, $C, $M) = map int, @ARGV;
}
my @c = (($C) x ($R-1), $C-$M);
my @m = map { (1<<$_)-1 } @c;
T: for my $t (0 .. $m[0]) {
	my @b; my @l = @m;
	for my $r (0 .. $R-1) {
		my $b = $b[$r] = $r <= 0 ? $t : $m[$r] & $l[$r-1];
		$r+1 < $R and $l[$r+1] ^= $m[$r+1] & $b;
		$l[$r] ^= $m[$r] & ($b<<1 ^ $b ^ $b>>1);
		0 <= $r-1 and $l[$r-1] ^= $m[$r-1] & $b;
	}
	0 == $l[$R-1] && 0 == $l[$R-2] or next T;
	say "Found solution: [";
	for my $r (0 .. $R-1) {
		for my $c (0 .. $C-1) {
			print " ", ($c[$r] <= $c ? " " : $b[$r]>>$c & 1 ? "P" : ".");
		}
		if (0) {
			print "  > ";
			for my $c (0 .. $C-1) {
				print " ", ($c[$r] <= $c ? " " : $l[$r]>>$c & 1 ? "*" : ".");
			}
		}
		say "";
	}
	say "]";
}
say "done searching (R=$R, C=$C, M=$M).";
__END__