3. Let n = 21-1 for some positive integer I. Suppose someone claims to hold an unsorted array A[1..n] of distinct l-bit strings; thus, exactly one l-bit string does not appear in A Suppose further that the only way we can access A is by calling the function FETCHBIT(i, j), which returns the jth bit of string Ali] in o(1) time. Describe a recursive algorithm to find the missing string in A using only O(n) calls to FETCHBIT