diogenysos: you wanted to say that plow HAS to remove two numbers ? right ? no matter how long is the path ? I think it's s a trap ... look at the diagonal, for example ... there are two numbered squares at the other end that plow resides ... so the plow has to go along the whole diagonal to get the numbered squares, simply because, empty squares do not count ? No, it wasn't my idea. Plow moves 2 squares no matter what ... thanks for your comments ...
Andy.