vi Contents

S7. Problems of Section 7 204

S8. Problems of Section 8 204

S9. Problems of Section 9 216

S10. Problems of Section 10 221

S11. Problems of Section 11 224

S12. Problems of Section 12 230

S13. Problems of Section 13 230

S15. Problems of Section 15 234

Appendix A. Elementary Number Theory 237

A.1. Modular arithmetic and rings 237

A.2. Greatest common divisor and unique factorization 239

A.3. Chinese remainder theorem 241

A.4. The structure of finite Abelian groups 243

A.5. The structure of the group

(Z/qZ)∗

245

A.6. Euclid’s algorithm 247

A.7. Continued fractions 248

Bibliography 251

Index 255