laymax = lambda x: (2 * x + 1) ** 2

def isp(x):
  if x == 2:
    return True
  if x <= 1 or x & 1 == 0:
    return False
  for i in xrange(3, int(x ** 0.5) + 1, 2):
    if x % i == 0:
      return False
  return True

be = 3
non = 2

i = 2
while 9 * be >= non:
  tmp = laymax(i)
  for j in xrange(4):
    #print float(be) / (be + non)
    if isp(tmp):
      be += 1
    else:
      non += 1
    tmp -= 2 * i
  i += 1

print 2 * i - 1