Minimum Changes to Make a K-Periodic Palindromic Password

Problem: Minimum Changes to Make a K-Periodic Palindromic Password Given a password string password of length n and an integer k. In one operation, you may change any character in password to any lowercase English letter. Return the minimum number of character changes needed so that the new password satisfies both conditions: The new password is k-periodic: for every index i such that i + k < n, password[i] == password[i + k]. The period pattern of length k is a palindrome: for every 0 <= r < k, the character at offset r in the period equals the character at offset k - 1 - r. Equivalently, for each index i, all characters whose index modulo k is either i % k or k - 1 - (i % k) must become the same character. Input Format n k password Output Format Print one integer: the minimum number of changes. Constraints 1 <= k <= n <= 2 * 10^5 password contains only lowercase English letters 'a' to 'z' Example 1 8 4 abcaabda Output: 2 Example Input 8 4 abcaabda Output 2