Extract Characters Around Word

Background

In a string processing scenario, you need to identify the occurrences of a specific word within a long string and extract the characters immediately before and after these words.

Problem Description

Given a main string and a non-empty word string, return a new string composed of the character immediately preceding and the character immediately following each appearance of the given word in the main string. Ignore cases where there is no character before or after the word. A character may be included twice if it is positioned between two occurrences of the word.

Input Format

Input is given from standard input in the following format.

S W

Where S is the main string and W is the word string. S and W are separated by a space.

Output Format

Output is printed to standard output in the following format.

result_string

Where result_string is the new string composed of extracted characters according to the problem requirements.

Sample

abcXY123XYijk XY

c13i

XY123XY XY

13

XY1XY XY

11

Sample Explanation

Sample 1: Main string S = "abcXY123XYijk", word string W = "XY".

1. The first XY appears at index 3. The character before it is 'c', and the character after it is '1'. Current result: "c1".
2. The second XY appears at index 8. The character before it is '3', and the character after it is 'i'. Final result: "c13i".

Sample 2: Main string S = "XY123XY", word string W = "XY".

1. The first XY appears at index 0. There is no character before it. The character after it is '1'. Current result: "1".
2. The second XY appears at index 5. The character before it is '3'. There is no character after it. Final result: "13".

Sample 3: Main string S = "XY1XY", word string W = "XY".

1. The first XY appears at index 0. There is no character before it. The character after it is '1'. Current result: "1".
2. The second XY appears at index 3. The character before it is '1'. There is no character after it. Final result: "11".

Constraints

Time limit: 1 second, Memory limit: 1024 KiB for each test case.