Given an array `intervals` where `intervals[i] = [li, ri]` represent the interval `[li, ri)`, remove all intervals that are covered by another interval in the list.

The interval `[a, b)` is covered by the interval `[c, d)` if and only if `c <= a` and `b <= d`.

Return the number of remaining intervals.

Example 1:

    Input: intervals = [[1,4],[3,6],[2,8]]
    Output: 2
    Explanation: Interval [3,6] is covered by [2,8], therefore it is removed.

Example 2:

    Input: intervals = [[1,4],[2,3]]
    Output: 1

Constraints:

- `1 <= intervals.length <= 1000`
- `intervals[i].length == 2`
- `0 <= li < ri <= 105`
- All the given intervals are unique.