给出两个数 a 和 b (0 <= a <= b <= 10^10000)，求 a 到 b 之间(包括a和b)的数字中，有多少个数字是包含9的（例如 19，910 等都是包含9的数字）。-Given two numbers a and b (0 < = a < = b < = 10 ^ 10000), seeking a between b (including a and b) the number, how many digits are contained 9 (for example, 19 , 910, etc. are number 9).