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(11,15).
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(20,24).
next(24,25).
next(25,26).
next(26,27).
next(27,28).
next(28,29).
next(29,30).
next(30,31).
next(28,32).
next(32,33).
next(33,34).
next(34,35).
next(32,36).
next(36,37).
next(37,38).
next(27,39).
next(39,40).
doAt(startflow,3).
doAt(a13,5).
doAt(a1,6).
doAt(a8,7).
doAt(a19,8).
doAt(a3,9).
doAt(a25,10).
doAt(a22,11).
doAt(a17,12).
doAt(endflow,13).
doAt(a18,15).
doAt(a7,16).
doAt(a14,17).
doAt(a24,18).
doAt(a15,19).
doAt(a9,20).
doAt(a20,21).
doAt(endflow,22).
doAt(a23,24).
doAt(a12,25).
doAt(a6,26).
doAt(a4,27).
doAt(a5,28).
doAt(a2,29).
doAt(endflow,30).
doAt(a16,32).
doAt(a11,33).
doAt(endflow,34).
doAt(a21,36).
doAt(endflow,37).
doAt(endflow,39).
subsAt(a13,4).
leftrightnexts(33,36).
leftrightnexts(29,32).
leftrightnexts(28,39).
leftrightnexts(21,24).
leftrightnexts(12,15).