A. x
Consider each quality factor.
This then has prime factors of all numbers are to be divided into a set.
This does not have prime factors of the number may have two options.
The prime factors of each case together with disjoint-set maintenance at China Unicom block number,
The answer is $ 2 ^ {cnt} -2 $
B. y
Dp violence is designed to be simple, it is clear what this can be used to optimize bitset dp, and then to change the way the card often seems to A?
It is clear that the number of states with 01 strings d growth is exponential, more and more difficult to transfer.
You may wish to use meet in the mid thought,
The dp20 bit of violence, only instead of dp10 bit.
Links point to enumerate the two states merged.
C. z
Thinking positive solutions probably will be asked to sort offline.
Taking into account some of the requirements is useless:
If $ $ x_i is sandwiched $ x_ {i-1} $ and $ x_ {i + 1} $ intermediate, the point i is useless.
If the current inquiry, while covering segment has $ $ x_i directly cover $ x_ {i + 1} $, then the bit is useless.
If you combine all the useless points, then the answer for a certain length can be expressed as a function of the form.
So with a small root useless heap constantly merge point, a maintenance function.
However, it seems difficult to play, but with no success