（狸捉兔子）围绕着山顶有10个洞，狐狸想要吃兔子，兔子说：“可以，但必须找到我，我就藏身于这10个洞中，你从10号洞出发，先到1号洞找，第二次隔1个洞找，第三次隔2个洞找，以后如此类推，次数不限。”但狐狸从早到晚进进出出了1000次，仍没有找到兔子。问兔子究竟藏在哪个洞里？((fox hunting rabbits) around the 10 hole in the top of the hill, the fox wanted to eat the rabbit, the rabbit said: "you can, but must find me, I will hide in the 10 hole, you start from No. 10 to No. 1 hole, second hole, hole every 1 for every 2, third find a hole, so after class, with no limit on the number of." But the fox came and out 1000 times from morning to night, and still didn't find a rabbit. Which hole is the rabbit hidden in?)