The counters may be arranged in this order:--

A1, B2, C3, D4, E5, F6, G7.

F4, G5, A6, B7, C1, D2, E3.

D7, E1, F2, G3, A4, B5, C6.

B3, C4, D5, E6, F7, G1, A2.

G6, A7, B1, C2, D3, E4, F5.

E2, F3, G4, A5, B6, C7, D1.

C5, D6, E7, F1, G2, A3, B4.

Amusements in Mathematics · 第 834 / 970 题