Give a divide-and-conquer algorithm with a time complexity of O(log n) to find the Single Letter. Finding the Single Letter: Given a string where all unique letters are supposed to appear twice one after one (e.g., bb). There may occur an error where one letter appears only once. Can you find the position of that single letter? Inputs with more than one single letter (e.g., bbeddf) or letters occurring more than twice (e.g., bbbb) are considered invalid. Examples: Input ccddebbffgg returns 4 Input aabbcc returns None Input aabbccdde returns 8 1) the pseudocode of your divide-and-conquer algorithm in the prologue docstrings 2) the explanation of its complexity in the prologue docstrings 3) a Python function find_single that implements your algorithm.