Busiest Hour

**Description:** A cafe has n chairs and q visitors; visitor i occupies the time interval [l_i, r_i] (inclusive, in minutes). What is the maximum number of visitors present at the same minute? **Input:** Line 1: n q (1 <= n <= 10^6, 1 <= q <= 2*10^5). Next q lines: l r (1 <= l <= r <= n). **Output:** One integer — the maximum concurrent visitors. **Example:** 10 2 / 1 3 / 2 5 -> 2 (minute 2 or 3).