Given a string, find the longest palindromic substring. Output should be the longest palindromic substring.
The longest palindromic substring in the input string "aabbacdbabefg" is "abba".
"aabbacdbabefg"
Below is an instruction that describes a task, paired with an input that provides further context. Write a response that appropriately completes the request.

### Instruction:
Given a string, find the longest palindromic substring. Output should be the longest palindromic substring.

### Input:
"aabbacdbabefg"

### Response:
The longest palindromic substring in the input string "aabbacdbabefg" is "abba".