next(1,2).
next(2,3).
next(3,4).
next(4,5).
next(5,6).
next(6,7).
next(4,8).
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(18,22).
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(28,32).
next(32,33).
next(33,34).
next(34,35).
next(35,36).
next(23,37).
next(37,38).
next(38,39).
doAt(startflow,3).
doAt(a11,4).
doAt(a15,5).
doAt(endflow,6).
doAt(a16,8).
doAt(a6,9).
doAt(a21,10).
doAt(a1,11).
doAt(a5,12).
doAt(a10,13).
doAt(a13,14).
doAt(a19,15).
doAt(a14,16).
doAt(a2,17).
doAt(a23,18).
doAt(a7,19).
doAt(endflow,20).
doAt(a20,22).
doAt(a18,23).
doAt(a22,24).
doAt(a9,25).
doAt(endflow,26).
doAt(a8,28).
doAt(a12,29).
doAt(endflow,30).
doAt(a3,32).
doAt(a17,33).
doAt(a4,34).
doAt(endflow,35).
doAt(a25,37).
doAt(endflow,38).
leftrightnexts(29,32).
leftrightnexts(25,28).
leftrightnexts(24,37).
leftrightnexts(19,22).
leftrightnexts(5,8).