You are given an `m x n` matrix `M` initialized with all `0`'s and an array of operations `ops`, where `ops[i] = [ai, bi]` means `M[x][y]` should be incremented by one for all `0 <= x < ai` and `0 <= y < bi`.

Count and return the number of maximum integers in the matrix after performing all the operations.

Example 1:

    Input: m = 3, n = 3, ops = [[2,2],[3,3]]
    Output: 4
    Explanation: The maximum integer in M is 2, and there are four of it in M. So return 4.

Example 2:

    Input: m = 3, n = 3, ops = [[2,2],[3,3],[3,3],[3,3],[2,2],[3,3],[3,3],[3,3],[2,2],[3,3],[3,3],[3,3]]
    Output: 4

Example 3:

    Input: m = 3, n = 3, ops = []
    Output: 9

Constraints:

- `1 <= m, n <= 4 * 104`
- `0 <= ops.length <= 104`
- `ops[i].length == 2`
- `1 <= ai <= m`
- `1 <= bi <= n`