13 13 1 ## cyclic group
abcdefghijklm
bcdefghijklma
cdefghijklmab
defghijklmabc
efghijklmabcd
fghijklmabcde
ghijklmabcdef
hijklmabcdefg
ijklmabcdefgh
jklmabcdefghi
klmabcdefghij
lmabcdefghijk
mabcdefghijkl