P9502 "MGOI" Simple Round I | A. Magic Number

> The more determined a mage is, the luckier they are. — Hall Mage S.

The magic number of the junior mage Xiao M is $2$. Given a positive integer $n$, Xiao M needs to find the largest **even** integer $m$ such that $2^m < n$. Please help him.

One line containing one positive integer $n$.

One line containing one **even** integer $m$, which is the answer.

**Constraints** For the first $20\%$ of the testdata, $n = 2$. For the first $60\%$ of the testdata, $n$ is a power of $2$. For $100\%$ of the testdata, $2 \le n \le 10^9$. Translated by ChatGPT 5