Given N intervals of the form [A, B]. The task is to return the maximum number of overlap among these intervals at any time.
Example 1:
Input:
N = 3
Intervals[] = {{1, 2}, {2, 4}, {3, 6}}
Output:
2
Explanation:
The maximum overlapping is 2(between (1 2) and
(2 4) or between (2 4) and (3 6))
Example 2:
Input:
N = 4
Intervals[] = {{1, 8}, {2, 5}, {5, 6}, {3, 7}}
Output:
4
Explanation:
The maximum overlapping is 4 (between (1, 8),
(2, 5), (5, 6) and (3, 7))

Your Task:
You don't need to read input or print anything. Your task is to complete the function overlap() which takes a list of pairs as input and returns an integer as output.

Expected Time Complexity: O(N * log N)
Expected Auxiliary Space: O(N)

Constraints:
2 <= N <= 2 * 10^{4}
1<= intervals[i][0] < intervals[i][1] <= 4*10^{3}

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