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(14,15).
next(15,16).
next(10,17).
next(17,18).
next(18,19).
next(19,20).
next(20,21).
next(21,22).
next(17,23).
next(23,24).
next(24,25).
next(25,26).
next(26,27).
next(27,28).
next(28,29).
doAt(startflow,4).
doAt(a11,6).
doAt(a5,7).
doAt(a4,8).
doAt(a3,9).
doAt(a8,10).
doAt(a15,11).
doAt(a7,12).
doAt(a6,13).
doAt(a14,14).
doAt(endflow,15).
doAt(a1,17).
doAt(a2,18).
doAt(a6,19).
doAt(a14,20).
doAt(endflow,21).
doAt(a13,23).
doAt(a10,24).
doAt(a12,25).
doAt(a6,26).
doAt(a14,27).
doAt(endflow,28).
compAt(a5,x2,5).
leftrightnexts(18,23).
leftrightnexts(11,17).