s1 <-> s3
s1 <-> s4
s1 <-> s5
s2 <-> s4
s2 <-> s5
s2 <-> s6
s7 <-> s8
s3 <-> s7
s4 <-> s7
s5 <-> s7
s6 <-> s7
s8 <-> s9
s8 <-> s10
s8 <-> s11
s8 <-> s12
s6 <-> s9
s8 <-> s13
s5 <-> s13
s5 <-> s11
s14 <-> s15
s8 <-> s14
s15 <-> s16
s15 <-> s17
s15 <-> s18
s15 <-> s19
s9 <-> s16
s9 <-> s17
s9 <-> s18
s11 <-> s19
s20 <-> s21
s15 <-> s20
s21 <-> s22
s21 <-> s23
s21 <-> s24
s21 <-> s25
s21 <-> s26
s21 <-> s27
s16 <-> s22
s17 <-> s22
s17 <-> s23
s18 <-> s23
s17 <-> s25
s16 <-> s24
s18 <-> s25
s28 <-> s29
s30 <-> s31
s32 <-> s33
s34 <-> s35
s36 <-> s37
s38 <-> s39
s40 <-> s41
s42 <-> s43
s44 <-> s45
s46 <-> s47
s22 <-> s28
s24 <-> s28
s23 <-> s32
s24 <-> s32
s24 <-> s38
s23 <-> s42
s25 <-> s42
s25 <-> s46
s25 <-> s32
s23 <-> s46
s23 <-> s44
s25 <-> s44
s23 <-> s40
s25 <-> s36
s21 <-> s30
s21 <-> s48
s21 <-> s49
s21 <-> s51
s21 <-> s50
s24 <-> s34
s45 <-> s52
s31 <-> s52
s49 <-> s52
s50 <-> s52
s51 <-> s52
s48 <-> s52
s37 <-> s52
s41 <-> s52
s35 <-> s52
s29 <-> s52
s47 <-> s52
s43 <-> s52
s39 <-> s52
s33 <-> s52