# 程序设计能力实训

1194. Prime

A prime is the number which can be only divide exactly by $1$ or itself.

### 输入格式

There several test case. Each test case have two positive integer $N,M$ in one line. $(0

### 输出格式

For each test case, output one line that contain an integer that is the number of primes from $N$ to $M$.

### 样例

Input
5 10
1 3
6 8

Output
2
2
1