Savchenko is technically still under copyright, though many international students use it under fair use for education. Mir Publishers (Moscow) holds the rights. However, since the book is out of print in many countries, finding a legal, high-quality version is tricky.
Many problems can be solved in two lines if you find the right "trick" or frame of reference, whereas a brute-force approach might take pages.
If you truly want the "better" PDF, buy a used physical copy from Abebooks or eBay (look for Mir Publishers, 1980s editions). Scan it at 600 DPI using a document feeder. This is the only way to guarantee perfection.
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