Given two strings s1, s2, find the lowest ASCII sum of deleted characters to make two strings equal.
- Input: s1 = "sea", s2 = "eat"
- Output: 231
- Explanation: Deleting "s" from "sea" adds the ASCII value of "s" (115) to the sum. Deleting "t" from "eat" adds 116 to the sum. At the end, both strings are equal, and 115 + 116 = 231 is the minimum sum possible to achieve this.