def is_prime(n: int) -> bool:
"""Primality test using 6k+-1 optimization."""
import math
if n <= 3:
return n > 1
if n % 2 == 0 or n % 3 == 0:
return False
i = 5
while i <= math.sqrt(n):
if n % i == 0 or n % (i + 2) == 0:
return False
i += 6
return True
def is_prime(n: int) -> bool:
"""Primality test using 6k+-1 optimization."""
if n <= 3:
return n > 1
if n % 2 == 0 or n % 3 == 0:
return False
i = 5
while i ** 2 <= n:
if n % i == 0 or n % (i + 2) == 0:
return False
i += 6
return True