Given a 1-indexed array of integers `numbers` that is already sorted in non-decreasing order, find two numbers such that they add up to a specific `target` number. Let these two numbers be `numbers[index1]` and `numbers[index2]` where `1 <= index1 < index2 <= numbers.length`.

Return the indices of the two numbers, `index1` and `index2`, added by one as an integer array `[index1, index2]` of length 2.

The tests are generated such that there is exactly one solution. You may not use the same element twice.

Your solution must use only constant extra space.

Example 1:

    Input: numbers = [2,7,11,15], target = 9
    Output: [1,2]
    Explanation: The sum of 2 and 7 is 9. Therefore, index1 = 1, index2 = 2. We return [1, 2].

Example 2:

    Input: numbers = [2,3,4], target = 6
    Output: [1,3]
    Explanation: The sum of 2 and 4 is 6. Therefore index1 = 1, index2 = 3. We return [1, 3].

Example 3:

    Input: numbers = [-1,0], target = -1
    Output: [1,2]
    Explanation: The sum of -1 and 0 is -1. Therefore index1 = 1, index2 = 2. We return [1, 2].

Constraints:

- `2 <= numbers.length <= 3 * 104`
- `-1000 <= numbers[i] <= 1000`
- `numbers` is sorted in non-decreasing order.
- `-1000 <= target <= 1000`
- The tests are generated such that there is exactly one solution.