Three examples that encode the n-queens problem. The third example calculates
solutions for different board sizes, which can be given as a list of intervals
on the command line.

Example calls:
    clingo queens1.lp
    clingo queens2.lp
    clingo incqueens.lp incqueens-py.lp -c calls="list((1,1),(3,5),(8,9))"
    clingo incqueens.lp incqueens-lua.lp -c calls="list((1,1),(3,5),(8,9))"

