Given a 7x7 grid of letters {a..g}, some cells are pre-filled. Fill the rest so that:
1) Each row has exactly one of each letter {a..g}.
2) Each column has exactly one of each letter {a..g}.
3) All cells on the minor diagonal (top-right to bottom-left) contain the same letter.

Here is the puzzle (each row on its own line, cells separated by commas, empty cells blank):

,b,,,a,,f
,d,g,,c,,
d,g,,c,f,e,b
,,,f,,b,
a,,f,e,,d,g
c,,,,d,,
f,,b,d,,,

Return the answer with the format:
<<<
row1
row2
...  (7 rows total)
>>>

where each row has 7 letters separated by commas.
