:- use_module(library(clpz)).
:- use_module(library(reif)).
:- use_module(library(pairs)).
:- use_module(library(lists)).

r_div(A,B,true):-A mod B#=0.
r_div(A,B,false):-A mod B#>0.

np_(C,Cp,N,P):-
  if_(=(N,1),
    P=C,
  	if_(
    	r_div(N,Cp),
    	(Q#=N/Cp,D#=C+1,np_(D,Cp,Q,P)),
    	(Np#=Cp+1,np_(C,Np,N,P))
  	)
  ).
np(N,P):-np_(0,2,N,P).
ch2(A,S):-maplist(np,A,B),pairs_keys_values(P,B,A),keysort(P,Q),pairs_values(Q,S).