Primes#3843
Let and (2 \le m < n \le 10^7) be integers. Consider the following set:
Determine the cardinality of the set Prime(m, n).
The input consists of several tests. The data for each test is given on a separate line as two integers and separated by a space. Any two consecutive tests are separated by an empty line.
For each test, output the answer on a separate line. Answers for different tests should be separated by an empty line. For each test, output the cardinality of the set Prime(m, n).
Example 1