You want to water `n` plants in your garden with a watering can. The plants are arranged in a row and are labeled from `0` to `n - 1` from left to right where the `ith` plant is located at `x = i`. There is a river at `x = -1` that you can refill your watering can at.

Each plant needs a specific amount of water. You will water the plants in the following way:

- Water the plants in order from left to right.
- After watering the current plant, if you do not have enough water to completely water the next plant, return to the river to fully refill the watering can.
- You cannot refill the watering can early.

You are initially at the river (i.e., `x = -1`). It takes one step to move one unit on the x-axis.

Given a 0-indexed integer array `plants` of `n` integers, where `plants[i]` is the amount of water the `ith` plant needs, and an integer `capacity` representing the watering can capacity, return the number of steps needed to water all the plants.

Example 1:

    Input: plants = [2,2,3,3], capacity = 5
    Output: 14
    Explanation: Start at the river with a full watering can:
    - Walk to plant 0 (1 step) and water it. Watering can has 3 units of water.
    - Walk to plant 1 (1 step) and water it. Watering can has 1 unit of water.
    - Since you cannot completely water plant 2, walk back to the river to refill (2 steps).
    - Walk to plant 2 (3 steps) and water it. Watering can has 2 units of water.
    - Since you cannot completely water plant 3, walk back to the river to refill (3 steps).
    - Walk to plant 3 (4 steps) and water it.
    Steps needed = 1 + 1 + 2 + 3 + 3 + 4 = 14.

Example 2:

    Input: plants = [1,1,1,4,2,3], capacity = 4
    Output: 30
    Explanation: Start at the river with a full watering can:
    - Water plants 0, 1, and 2 (3 steps). Return to river (3 steps).
    - Water plant 3 (4 steps). Return to river (4 steps).
    - Water plant 4 (5 steps). Return to river (5 steps).
    - Water plant 5 (6 steps).
    Steps needed = 3 + 3 + 4 + 4 + 5 + 5 + 6 = 30.

Example 3:

    Input: plants = [7,7,7,7,7,7,7], capacity = 8
    Output: 49
    Explanation: You have to refill before watering each plant.
    Steps needed = 1 + 1 + 2 + 2 + 3 + 3 + 4 + 4 + 5 + 5 + 6 + 6 + 7 = 49.

Constraints:

- `n == plants.length`
- `1 <= n <= 1000`
- `1 <= plants[i] <= 106`
- `max(plants[i]) <= capacity <= 109`