Problem

You are given an integer array nums and a list of operations. Each operation is a range update of the form [l, r, val], meaning you may apply it to decrease every element in nums[l...r] by val once.

Your task is to determine the minimum number of operations from the start of the list that must be applied so that every element of the array becomes exactly 0. If it is impossible to reach an all-zero array using all operations, return -1.

The key challenge is to decide, for a given prefix of operations, whether that prefix is sufficient to reduce every position to zero without making any value negative in a way that violates the target.

Input Format

• An integer array nums
• An array of operations, where each operation is [l, r, val]

Output Format

• Return the minimum number of operations from the front of the list required to transform nums into an all-zero array.
• Return -1 if no prefix of the operations works.

Constraints

• 1 <= nums.length <= $10^{5}$
• 0 <= nums[i] <= $10^{9}$
• 1 <= operations.length <= $10^{5}$
• 0 <= l <= r < nums.length
• 1 <= val <= $10^{9}$

Notes

• Operations are considered in the given order.
• You only need to determine whether a prefix of operations is enough; you do not need to find the exact subset of operations.
• Efficient solutions typically test prefixes with a range-accumulation data structure.