for (int idx = 0; idx < 10; idx++)
for (Square s1 = SQ_A1; s1 <= SQ_D4; ++s1)
if (MapA1D1D4[s1] == idx && (idx || s1 == SQ_B1)) // SQ_B1 is mapped to 0
for (int idx = 0; idx < 10; idx++)
for (Square s1 = SQ_A1; s1 <= SQ_D4; ++s1)
if (MapA1D1D4[s1] == idx && (idx || s1 == SQ_B1)) // SQ_B1 is mapped to 0