You are given a strictly increasing integer array `rungs` that represents the height of rungs on a ladder. You are currently on the floor at height `0`, and you want to reach the last rung.

You are also given an integer `dist`. You can only climb to the next highest rung if the distance between where you are currently at (the floor or on a rung) and the next rung is at most `dist`. You are able to insert rungs at any positive integer height if a rung is not already there.

Return the minimum number of rungs that must be added to the ladder in order for you to climb to the last rung.

Example 1:

    Input: rungs = [1,3,5,10], dist = 2
    Output: 2
    Explanation:
    You currently cannot reach the last rung.
    Add rungs at heights 7 and 8 to climb this ladder.
    The ladder will now have rungs at [1,3,5,7,8,10].

Example 2:

    Input: rungs = [3,6,8,10], dist = 3
    Output: 0
    Explanation:
    This ladder can be climbed without adding additional rungs.

Example 3:

    Input: rungs = [3,4,6,7], dist = 2
    Output: 1
    Explanation:
    You currently cannot reach the first rung from the ground.
    Add a rung at height 1 to climb this ladder.
    The ladder will now have rungs at [1,3,4,6,7].

Constraints:

- `1 <= rungs.length <= 105`
- `1 <= rungs[i] <= 109`
- `1 <= dist <= 109`
- `rungs` is strictly increasing.