Sessionise the clickstream

A product-analytics team in Sao Paulo receives raw website events as HH:MM:SS user page (one day only). The events are not sorted. They want to know how users really behave in sessions.

For each user, sort that user's events by time. A new session starts at the user's first event, and also whenever the gap between two consecutive events (in time order) is strictly greater than G minutes. The duration of a session is its last event time minus its first event time, in seconds (a session with a single event lasts 0 seconds). Events with exactly the same second belong to the same session.

Task: line 1 is G, line 2 is N, then N event lines. For each user in alphabetical order (case-sensitive) print user sessions=S total=T longest=L pages=P, where S is the number of sessions, T the sum of all session durations, L the longest session duration and P the number of distinct pages the user visited overall.