Plusle and Minun on Array

Chef has an array $A$ of length $N$. He defines the *alternating sum* of the array as: - $S = |A_1| - |A_2| + |A_3| - |A_4| + \ldots (-1)^{N-1}\cdot |A_N|$ Chef is allowed to perform the following operation on the array **at most once**: - Choose two indices $i$ and $j$ $(1 \leq i < j \leq N)$ and swap the elements $A_i$ and $A_j$. Find the **maximum** *alternating sum* Chef can achieve by perf