Residue class
From AoPSWiki
In modular arithmetic, a residue of an integer 
in modulo 
is the unique value of 
such that 
. In the context of division, a residue is simply a remainder.
A residue class is a complete set of integers that are congruent modulo for some positive integer . In modulo , there are exactly different residue classes, corresponding to the possible residues 
Each residue class contains all integers in the form 
where 
is the corresponding residue.
