Question 15
The factorial $n!=n(n-1)\cdots1$ is the product of the first $n$ positive integers; for example, $2!=2\times1$ and $7!=7\times6\times5\times4\times3\times2\times1$. How many integers from 1 to 40 cannot be the number of consecutive zeros at the end of $n!$, for any positive integer $n$?