Say that a pattern P of length m is a circular substring of a text T of length n > m if P is a (normal) substring of T, or if P is equal to the concatenation of a suffix of T and a prefix of T, that is, if there is an index 0 ≤ k < m, such that P = T[n−m+k..n−1]+T[0..k−1]. Give an O(n+m)-time algorithm for determining whether P is a circular substring of T.