Reverse Every Other Chunk

Difficulty: 1200 2000 ms 128 MB

strings

Split S into blocks of 2K; in each block reverse the FIRST K characters and keep the next K as they are (short tails: reverse what exists of the first K).

Input: the first line has S; the second line has K.

Output: the transformed string.

Constraints:

• 1 ≤ |S| ≤ 10⁴
• 1 ≤ K ≤ |S|

Sample Tests

abcdefg
2

bacdfeg

abcd
4

dcba

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