Find Maximum Value in a Constrained Sequence

Description

You are given an integer n, a 2D integer array restrictions, and an integer array diff of length n - 1. Your task is to construct a sequence of length n, denoted by a[0], a[1], ..., a[n - 1], such that it satisfies the following conditions:

- a[0] is 0.

- All elements in the sequence are non-negative.

- For every index i (0 <= i <= n - 2), abs(a[i] - a[i + 1]) <= diff[i].

- For each restrictions[i] = [idx, maxVal], the value at position idx in the sequence must not exceed maxVal (i.e., a[idx] <= maxVal).

Your goal is to construct a valid sequence that maximizes the largest value within the sequence while satisfying all the above conditions.

Return an integer denoting the largest value present in such an optimal sequence.