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(16,17).
next(17,18).
next(18,19).
next(19,20).
next(20,21).
next(21,22).
next(22,23).
next(23,24).
next(21,25).
next(25,26).
next(26,27).
next(27,28).
next(28,29).
next(29,30).
next(27,31).
next(31,32).
next(32,33).
next(33,34).
next(20,35).
next(35,36).
next(19,37).
next(37,38).
doAt(startflow,3).
doAt(a15,5).
doAt(a21,6).
doAt(a16,7).
doAt(a22,8).
doAt(a5,9).
doAt(a4,10).
doAt(a10,11).
doAt(a1,12).
doAt(a18,13).
doAt(a25,14).
doAt(a3,15).
doAt(a7,16).
doAt(a8,17).
doAt(a11,18).
doAt(a14,19).
doAt(a24,20).
doAt(a13,21).
doAt(a23,22).
doAt(endflow,23).
doAt(a12,25).
doAt(a2,26).
doAt(a9,27).
doAt(a17,28).
doAt(endflow,29).
doAt(a19,31).
doAt(a6,32).
doAt(endflow,33).
doAt(endflow,35).
doAt(endflow,37).
subsAt(a15,4).
leftrightnexts(28,31).
leftrightnexts(22,25).
leftrightnexts(21,35).
leftrightnexts(20,37).