Change string A to B such that it has maximum LCS with K operation

We are given two strings A and B. We are only allowed to change A by increasing the char[i] to the next alphabet in the alphabet series a->b, b->c, z-> a. Or changing to the previous char b->a, a->z.
0 < A.len ,B.len < 100
a <= A[i], B[i] <= z
0 <= k <= 200.
we can use almost k such operations, and find the max lcs we can achieve.