Maestro n° 103 : Page 85 - Gr 82
r8c1 -6- r8c6 =6=8= r8c6 -8- r7c6 =8=2= r7c6 -2- r7c1 =2= r5c1 -2-1- r5c1 =1= r8c1 => r8c1 ≠ 6