12.2.65 Number theory
Condition: Find out which of these numbers are comparable modulo \( m \); check whether it is possible to construct a complete system of residues modulo \( m \) from these numbers. \[ \begin{array}{l} 253, \quad-130, \quad 512, \quad 84, \quad-40, \\ 124, \quad 59, \quad 176, \quad 503, \quad m=7 . \end{array}\]
A huge number of interesting olympiad problems in number theory, and its various sections.