Number of solutions: 1

Solution 1:
@bbbbbbbbcc@cc
abbddb@b@ccccc
@aa@dbbbbdeecc
aaddddd@ddgec@
aaa@fdddddg@cc
ahhff@f@gggeee
i@hhhfjjj@geee
ihhi@fkjjeeee@
i@iihkkjjj@len
iiiiikkj@jll@n
mm@mm@kkkjllnn
mmmmmkkkjj@j@n
mm@mmm@kknjjnn
mmmm@mmkk@nnnn