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):

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

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

where each row has 7 letters separated by commas.
