You are given a string s, a split is called good if you can split s into 2 non-empty strings p and q where its concatenation is equal to s and the number of distinct letters in p and q are the same. Return the number of good splits you can make in s. Example 1: Input: s = "aacaba" Output: 2 Explanation: There are 5 ways to split "aacaba" and 2 of them are good. ("a", "acaba") Left string and right string contains 1 and 3 different letters respectively. ("aa", "caba") Left string and right string contains 1 and 3 different letters respectively. ("aac", "aba") Left string and right string contains 2 and 2 different letters respectively (good split). ("aaca", "ba") Left string and right string contains 2 and 2 different letters respectively (good split). ("aacab", "a") Left string and right string contains 3 and 1 different letters respectively. Example 2: Input: s = "abcd" Output: 1 Explanation: Split the string as follows ("ab", "cd"). Example 3: Input: s = "aaaaa" Output: 4 Explanation: All possible splits are good. Example 4: Input: s = "acbadbaada" Output: 2 Constraints: s contains only lowercase English letters. 1 <= s.length <= 10^5