next(1,2).
next(2,3).
next(3,4).
next(4,5).
next(5,6).
next(6,7).
next(7,8).
next(4,9).
next(9,10).
next(10,11).
next(11,12).
next(12,13).
next(13,14).
next(14,15).
next(12,16).
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(24,28).
next(28,29).
next(29,30).
next(30,31).
next(31,32).
next(32,33).
next(33,34).
next(34,35).
next(32,36).
next(36,37).
next(37,38).
next(38,39).
doAt(startflow,3).
doAt(a16,4).
doAt(a11,5).
doAt(a17,6).
doAt(endflow,7).
doAt(a15,9).
doAt(a4,10).
doAt(a14,11).
doAt(a13,12).
doAt(a6,13).
doAt(endflow,14).
doAt(a10,16).
doAt(a24,17).
doAt(endflow,18).
doAt(a7,20).
doAt(a20,21).
doAt(a2,22).
doAt(a3,23).
doAt(a21,24).
doAt(a22,25).
doAt(endflow,26).
doAt(a8,28).
doAt(a19,29).
doAt(a23,30).
doAt(a1,31).
doAt(a25,32).
doAt(a12,33).
doAt(endflow,34).
doAt(a18,36).
doAt(a9,37).
doAt(endflow,38).
leftrightnexts(33,36).
leftrightnexts(25,28).
leftrightnexts(17,20).
leftrightnexts(13,16).
leftrightnexts(5,9).