删数问题，给定n位正整数a，去掉其中任意k个数字后，剩下的数字按原次序排列组成一个新的正整数。对于给定的n为正整数a和正整数k，设计一个算法找出剩下的数字组成的新数最小的删数方案-Cut a few problems, given n-bit positive integer a, removed one of arbitrary k-figures, the remaining number of the original order to form a new positive intege