Maestro n° 103 : Page 74 - Gr 71
r6c5 -3- r7c5 =3=6= r7c5 -6- r7c3 =6= r5c3 -6- r5c9 =6=7= r5c9 -7- r5c5 =7= r6c5 => r6c5 ≠ 3