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(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(27,28).
next(25,29).
next(29,30).
next(30,31).
next(31,32).
next(32,33).
next(33,34).
next(31,35).
next(35,36).
next(36,37).
next(24,38).
next(38,39).
doAt(startflow,3).
doAt(a4,4).
doAt(a19,5).
doAt(a25,6).
doAt(a14,7).
doAt(a17,8).
doAt(a3,9).
doAt(a15,10).
doAt(a21,11).
doAt(a10,12).
doAt(a6,13).
doAt(endflow,14).
doAt(a1,16).
doAt(a11,17).
doAt(endflow,18).
doAt(a5,20).
doAt(a2,21).
doAt(a16,22).
doAt(a22,23).
doAt(a18,24).
doAt(a8,25).
doAt(a7,26).
doAt(endflow,27).
doAt(a9,29).
doAt(a12,30).
doAt(a20,31).
doAt(a24,32).
doAt(endflow,33).
doAt(a23,35).
doAt(endflow,36).
doAt(endflow,38).
leftrightnexts(32,35).
leftrightnexts(26,29).
leftrightnexts(25,38).
leftrightnexts(17,20).
leftrightnexts(13,16).