Given three integers `x`, `y`, and `bound`, return a list of all the powerful integers that have a value less than or equal to `bound`.

An integer is powerful if it can be represented as `xi + yj` for some integers `i >= 0` and `j >= 0`.

You may return the answer in any order. In your answer, each value should occur at most once.

Example 1:

    Input: x = 2, y = 3, bound = 10
    Output: [2,3,4,5,7,9,10]
    Explanation:
    2 = 20 + 30
    3 = 21 + 30
    4 = 20 + 31
    5 = 21 + 31
    7 = 22 + 31
    9 = 23 + 30
    10 = 20 + 32

Example 2:

    Input: x = 3, y = 5, bound = 15
    Output: [2,4,6,8,10,14]

Constraints:

- `1 <= x, y <= 100`
- `0 <= bound <= 106`