Score : 1500 points
Shik's job is very boring. At day 0, his boss gives him a string S_0 of length N which consists of only lowercase English letters. In the i-th day after day 0, Shik's job is to copy the string S_{i-1} to a string S_i. We denote the j-th letter of S_i as S_i[j].
Shik is inexperienced in this job. In each day, when he is copying letters one by one from the first letter to the last letter, he would make mistakes. That is, he sometimes accidentally writes down the same letter that he wrote previously instead of the correct one. More specifically, S_i[j] is equal to either S_{i-1}[j] or S_{i}[j-1]. (Note that S_i[1] always equals to S_{i-1}[1].)
You are given the string S_0 and another string T.
Please determine the smallest integer i such that S_i could be equal to T. If no such i exists, please print -1
.
The input is given from Standard Input in the following format:
N S_0 T
Print the smallest integer i such that S_i could be equal to T. If no such i exists, print -1
instead.
5 abcde aaacc
2
S_0 = abcde
, S_1 = aaccc
and S_2 = aaacc
is a possible sequence such that S_2 = T.
5 abcde abcde
0
4 acaa aaca
2
5 abcde bbbbb
-1