$4 \cdot 52$ for some natural number $n, 2^{n}$ and $5^{n}$ have the same digit in their highest place, what is this digit?



Translating the text into English while preserving the original formatting and line breaks, the result is as follows:

$4 \cdot 52$ for some natural number $n, 2^{n}$ and $5^{n}$ have the same digit in their highest place, what is this digit?