单点时限: 2.0 sec
内存限制: 256 MB
A prime is the number which can be only divide exactly by $1$ or itself.
There several test case. Each test case have two positive integer $N,M$ in one line. $(0<N \leqslant M<10^6)$
For each test case, output one line that contain an integer that is the number of primes from $N$ to $M$.
5 10 1 3 6 8
2 2 1