风的记忆

一道技巧性的ＤＰ题，只要知道思路了很容易。

A common pastime for poker players at a poker table is to shuffle stacks of chips. Shuffling chips is performed by starting with two stacks of poker chips, S1 and S2, each stack containing C chips. Each stack may contain chips of several different colors.

Let x and y be two strings over some finite alphabet A. We would like to transform x into y allowing only operations given below: Deletion: a letter in x is missing in y at a corresponding position. Insertion: a letter in y is missing in x at a correspond