Delete distance

Given two strings word1 and word2, return the minimum number of single-character DELETIONS required (from either string) to make the two strings equal. Each step deletes exactly one character from one of the strings. 0 <= len(word1), len(word2) <= 500, lowercase letters. Example: 'sea' and 'eat' -> 2 (delete 's' and 't', both become 'ea').