P5720 [Deep Basics 4. Example 4] A One-Chi Stick

In *Zhuangzi*, it is said: “A one-chi stick, take half of it each day, and it will never be exhausted.” On the first day, there is a wooden stick of length $a$. Starting from the second day, each day you saw off half of the stick (divide by $2$ each time, rounding down). On which day will the length of the stick become $1$?

Input a positive integer $a$, representing the length of the stick.

Output a positive integer, representing on which day the length of the stick will become $1$.

Constraints: $1 \le a \le 10^9$. Translated by ChatGPT 5