1 a 
1   b
3 a b
2 a   c
2   b c 
4 a b    d

##</code><code>##

-max: 1	26
-max: 2	350
-max: 3	3247
-max: 4	23312
-max: 5	137909
-max: 6	698996
-max: 7	3116882
-max: 8	12461993
sum 16442715