Given a string A consisting of n characters and a string B consisting of m characters, write a function that will return the number of times A must be stated such that B is a substring of the repeated A. If B can never be a substring, return -1.
A = ‘abcd’
B = ‘cdabcdab’
The function should return 3 because after stating A 3 times, getting ‘abcdabcdabcd’, B is now a substring of A.
You can assume that n and m are integers in the range [1, 1000].