Counting Primes in a Range

You are given two integers $m$ and $n$ with $2 \le m < n \le 10\,000\,000$.

Consider the following set.

$\mathrm{Prime}(m, n) = \{\, p \mid p \in \mathbb{P},\ m \le p \le n \,\}$

Here $\mathbb{P}$ is the set of all primes, so $\mathrm{Prime}(m, n)$ collects every prime that is at least $m$ and at most $n$.

Compute the number of elements of $\mathrm{Prime}(m, n)$.

The input consists of several tests. Each test occupies one line and holds $m$ and $n$ separated by exactly one space. An empty line separates any two consecutive tests.

For each test, print the number of elements of $\mathrm{Prime}(m, n)$ on its own line, in the same order as the input. Print an empty line between any two consecutive results.