单点时限: 2.0 sec
内存限制: 256 MB
Give you an integer $n$, find the maximum $k$ that satisfies
$$n! \bmod 10^k = 0$$
There are several test cases, please process till
For each test case, there is only one line contains integer $n$ $(1 \leq n \leq 10^9)$.
For each test case, output the answer in one line.