Typo in Introduction to the Burrows-Wheeler Transform and FM Index

Thank you very much for the great tutorial on BW and FM! This is a great read. I think this is a type on Page 10, section 4, the third last line. 
`rankAll[c][i0] − x gives the same value we would have found in rankAll[c][i] − x`. 
I think the latter `-x` should be removed. 