Given a string s consists of some words separated by spaces, return the length of the last word in the string. If the last word does not exist, return 0. A word is a maximal substring consisting of non-space characters only. Example 1: Input: s = "Hello World" Output: 5 Example 2: Input: s = " " Output: 0 Constraints: 1 <= s.length <= 104 s consists of only English letters and spaces ' '.