from common import sieve

primes = sieve(30000).primes()
prime_list = list(primes)
prime_list.sort()

def is_prime(n):
	if n in primes:
		return True
	for p in prime_list:
		if p*p > n:
			return True
		if n % p == 0:
			return False
	return True

def count_primes(numbers):
	prime = 0
	for n in numbers:
		if is_prime(n):
			prime += 1
	return prime

#numbers = [1, 3, 5, 7, 9]
prime_count = 3
number_count = 5
level = 2
last = 9

while 10*prime_count >= number_count:
	step = 2 * level
	numbers = [last+step, last+2*step, last+3*step, last+4*step]
	prime_count += count_primes(numbers)
	number_count += 4
	level += 1
	last += 4*step

print 2*(level-1) + 1