Bitmasks
From charlesreid1
Java and bitmasks
The official line from Oracle: https://docs.oracle.com/javase/tutorial/java/nutsandbolts/op3.html
Useful answer, but documentation/refs please?? https://stackoverflow.com/questions/4549131/bitmask-question#4549243
Almost useful but poorly formatted: http://codeforces.com/blog/entry/18169