In this problem
http://www.codechef.com/problems/HOTEL
the 5th guest in the third sample input is arriving at 2 and leaving at 9 according to me there are 3 more guest arriving at the same time period ie. guest2 guest 3 and guest4
making the total count to 4 how come it is 3 ... pls help me to clear what a simultaneous stay is !!!