B'You are given two binary strings a and b of length n . In each move, the string a is modified in the following way. What is the expected number of moves required to make both strings equal for the first time? A binary string is a string, in which the character is either tt{0} or tt{1} . The first line contains a single integer t ( 1 <= q t <= q 10^5 ) -- the number of test cases. The description of the test cases follows. The first line of each test case contains a single integer n ( 1 <= q n <= q 10^6 ) -- the length of the strings. The second line of each test case contains the binary string a of length n . The third line of each test case contains the binary string b of length n . It is guaranteed that the sum of n over all test cases does not exceed 10^6 . For each test case, output a single line containing the expected number of moves modulo 998 ,244 ,353 . Formally, let M = 998 ,244 ,353 . It can be shown that the answer can be expressed as an irreducible fraction frac{p}{q} , where p and q are integers and q not equiv 0 pmod{M} . Output the integer equal to p cdot q^{-1} bmod M . In other words, output such an integer x that 0 <= x < M and x cdot q equiv p pmod{M} . In the first test case, index 1 is chosen randomly and a_1 is flipped. After the move, the strings a and b are equal. The expected number of moves is 1 . The strings a and b are already equal in the second test case. So, the expected number of moves is 0 . The expected number of moves for the third and fourth test cases are frac{56}{3} and frac{125}{3} respectively. '...