Maximize Equal Array Length After Contiguous Sum Merges

You are given two nonempty arrays of positive integers, `a` and `b`. In either array, you may replace a contiguous group of elements with one element equal to their sum. You may repeat this operation independently on both arrays. Implement `maxCommonLength(a, b)`. Return the maximum possible length of the resulting arrays when they are exactly equal, element by element. Return `-1` if they cannot be made equal. ### Rules and Constraints - Merging preserves element order. You may merge adjacent groups but cannot split an element, reorder elements, or remove values. - You may perform no operations on an array that already has the desired form. - Each array has between 1 and 100,000 elements. Every value is between 1 and 1,000,000,000. - Intermediate and total sums must be represented exactly. ### Example 1 ```text a = [1, 2, 3, 3] b = [3, 3, 3] Output: 3 ``` Merge the first two elements of `a` to obtain `[3, 3, 3]`. Length 3 is maximal because `b` starts with only three elements and merging cannot increase its length. ### Example 2 ```text a = [1, 2] b = [4] Output: -1 ``` No allowed sequence of merges makes these arrays equal.