通过计算的判断究竟在范围内有多少个质数的问题，怎么使用C语言的程序的编写的技术实现？

Problem Description
Easy question! Calculate how many primes between [1...n]!

Input
Each line contain one integer n(1 <= n <= 1e11).Process to end of file.

Output
For each case, output the number of primes in interval [1...n]

Sample Input
2
3
10

Sample Output
1
2
4