きったんの頭_ん中☆

#! /usr/bin/env python3
"""
pe10.py
https://mind.kittttttan.info/py/pe10
"""

def pe10(n=2000000):
    """
    Calculate the sum of all the primes below two million.
    """
    s = [True] * (n + 1)
    s[0], s[1] = False, False
    sq = int(n**0.5)
    for i in range(2, sq + 1):
        if s[i]:
            m = n//i - i
            s[i * i : n + 1 : i] = [False] * (m + 1)
    print(sum(i for i in range(n + 1) if s[i]))

if __name__ == "__main__":
    pe10()