Олимпиадный тренинг

Задача 39052. Let's count the numbers - 05


The value of an arithmetic expression
\(3 \cdot 4^{84} + 4 ^{83}- 4^{63} - 3 \cdot 4 ^{42}+4^{40} - 4^{38}+3\)
written in the number system with base 8. How many 7 digits does this entry contain?