# //Given a string s, return the longest palindromic substring in s.

# //Example 1:

# //Input: s = "babad"
# //Output: "bab"
# //Note: "aba" is also a valid answer.
# //Example 2:

# //Input: s = "cbbd"
# //Output: "bb"
# //Example 3:

# //Input: s = "a"
# //Output: "a"
# //Example 4:

# //Input: s = "ac"
# //Output: "a"
