设A和B是长度相同的2个字符串。A和B的距离定义为相应位置字符距离之和。2个非空格字符的距离是它们的ASCII码之差的绝对值。空格与空格的距离为0；空格与其它字符的距离为一定值k。

字符串A的扩展是在A中插入若干空格字符所产生的字符串。在字符串A和B的所有长度相同的扩展中，有一对距离最小的扩展，该距离称为字符串A和B的扩展距离。

对于给定的字符串A和B，试设计一个算法，计算其扩展距离。

-Let A and B is the same length of two strings. A and B is defined as the distance between the corresponding location and distance characters. Two non-space character, the distance between them is the ASCII of absolute poor. And the blank spaces in the range of 0; Space with other characters to a certain distance from the k value. A string of expansion is inserted in A certain space character from the string. In the A and B string in all the same length of the extension, a minimum distance of the expansion, The distance from the string as A and B from the expansion. For a given string, A and B, test design an algorithm to calculate the distance of expansion.