Any amount of white space may precede the first integer and any characters may follow the second integer. The first integer is the number of taxa. The second is the number of sites in the alignment. The data for each taxon comes in a block of lines. The first line contains the taxon name and optional comments.
Subsequent lines carry the sequence, optionally broken by white space.
There should not be any comments on the sequence data lines. Empty lines are allowed at any point in the data file. It is an error if the end of file occurs before all data is read. Sequence data may be upper or lower case. Case is irrelevant.