next(1,2).
next(2,3).
next(3,4).
next(4,5).
next(5,6).
next(6,7).
next(7,8).
next(8,9).
next(9,10).
next(10,11).
next(11,12).
next(12,13).
next(13,14).
next(11,15).
next(15,16).
next(16,17).
next(17,18).
next(18,19).
next(16,20).
next(20,21).
next(21,22).
next(22,23).
next(23,24).
next(24,25).
next(25,26).
next(26,27).
next(27,28).
doAt(startflow,5).
doAt(a14,8).
doAt(a12,10).
doAt(a15,11).
doAt(a11,12).
doAt(endflow,13).
doAt(a13,15).
doAt(a4,16).
doAt(a8,17).
doAt(endflow,18).
doAt(a9,20).
doAt(a1,21).
doAt(a6,22).
doAt(a5,23).
doAt(a10,24).
doAt(a7,25).
doAt(a2,26).
doAt(endflow,27).
compAt(a12,x2,6).
compAt(a14,x2,7).
subsAt(a12,9).
leftrightnexts(17,20).
leftrightnexts(12,15).