Combine at most two equal letters Ex = aab, aac ...... dee Of the set = a, b, c, d, and E

Combine at most two equal letters Ex = aab, aac ...... dee Of the set = a, b, c, d, and E also of the set = f, g, h, i
Ffg ..... hii
The matrix is this A b c d e
f 01 02 03 04 05
g06 07 08 09 10
h11 12 13 14 15
i 16 17 18 19 20