Upto where did Chandragupta Maurya's empire extend in the north west?

According to the Buddhist text Mahavamsa tika, Chandragupta and his guru Chanakya began recruiting an army after he completed his studies at Taxila (now in Pakistan). This was a period of wars, given that Alexander the Great had invaded the northwest subcontinent from Caucasus Indicus (also called Paropamisadae in ancient texts, now called the Hindu Kush mountain range).