"contact-portland-1-v2.dat" is a static person-person contact graph,
including the sublocation model. That is, contacts only exist between
people at the same location and sublocation.

Each line contains one contact between a pair of people. Note that two
people may be connected by more than one edge if they share several
activity types.  Contacts are bi-directional (i.e., if person A has a
contact with person B, then B has a contact of the same length with
A).  Only one direction is represented in the file, such that Person
Id 1 is always greater than Person Id 2.

Each line has the following fields:

Person Id 1 - Id of the first person of the contact pair
Purpose 1 - Activity purpose of the first person
Person Id 2 - Id of the second person of the contact pair
Purpose 2 - Activity purpose of the second person
Contact Duration - Time in seconds of the contact