Some boundaries you should know to approximate time and space complexity of your algorithm. $2^{10} = 1,024 \approx 10^{3}, 2^{20} = 1,048,576 \approx 10^{6}$ 32-bit signed integers (int) and 64-bit signed integers (long long) have upper limits of $2^{31} − 1 \approx 2 \times 10^{9}$ (safe for up to $\approx 9$ decimal digits) and $2^{63} − 1 \approx 9 \times 10^{18}$ (safe for up to $\approx 18$ decimal digits) respectively. Read more...