Give an input list,
Room number: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8
size: 3 | 2 | 5 | 6 | 7 | 8 | 9 | 3

Write a function findRoom(preferredNumber, minSize) to get the first room number, otherwise return -1;
preferredNumber and room number have little difference.
size >= minSize.