#!/usr/bin/env python
# coding=utf-8

# 给定一个数字 确定小于这个数字的 素数的个数

class Solution:
    
    def fermat_test(self):
        """费马检查 theta(logn)"""
        pass

    def smallest_divisor(self):
        """最小因子"""
        pass
    
    def is_prime(self, num):
        pass
    
    # @param {integer} n
    # @return {integer}
    def countPrimes(self, n):
        pass

        
sol = Solution()
sol.countPrimes(5000000)

