3744. Find Kth Character in Expanded String

You are given a string s consisting of one or more words separated by single spaces. Each word in s consists of lowercase English letters.

We obtain the expanded string t from s as follows:

• For each word in s, repeat its first character once, then its second character twice, and so on.

For example, if s = "hello world", then t = "heelllllllooooo woorrrllllddddd".

You are also given an integer k, representing a valid index of the string t.

Return the kth character of the string t.

Example 1:

Example 2:

Constraints:

• 1 <= s.length <= 105
• s contains only lowercase English letters and spaces ' '.
• s does not contain any leading or trailing spaces.
• All the words in s are separated by a single space.
• 0 <= k < t.length. That is, k is a valid index of t.