Feedback for AIRM problem

Problem Link: AIRM Problem - CodeChef


Suppose the arrival and departure times are
1 2 1
2 3 3

Let us say, (1,2) lands on airport 1, then (1,3) cannot land on airport 1, it must land on another airport, say airport 2. Now we are left with (2,3). Clearly, (2,3) can not land on either of (1,2) or (1,3). Thus we need another airport, say airport 3 for (2,3). Thus we would need a minimum of three airports for smooth landing of each of them. BUT, according to the code mentioned above the answer would be ‘2’ but there is no way that two airports can handle these flights. I wasted an hour on this problem just to find out that even the editorial is wrong!