Problem : Common Schedule
The Leaders of all countries around the world need to gather in order to sign the World Peace Summit.
Today is the D-Day. Given N countries and the schedule of their leaders for next 24 hours, your task is to find a maximum time slot such that all leaders are available during that period.
The first line contains N, the number of countries.
The following line contains:
1. I - unique id of the leader
2. [A , B) - the time slot when the leader is busy i.e. including time A, but excluding time B
End of input is given by "-1"
• Each country will have only one representative
• Time slot [A, B) will be in the format HH:MM