import typing

def inv_gcd(a: int, b: int) -> typing.Tuple[int, int]:
	a %= b
	if a == 0:
		return (b, 0)
	s = b
	t = a
	m0 = 0
	m1 = 1
	while t:
		u = s // t
		s -= t * u
		m0 -= m1 * u
		s, t = t, s
		m0, m1 = m1, m0
	if m0 < 0:
		m0 += b // s
	return (s, m0)

def inv_mod(x: int, m: int) -> int:
	z = inv_gcd(x, m)
	return z[1]

def crt(r: typing.List[int], m: typing.List[int]) -> typing.Tuple[int, int]:
	r0 = 0
	m0 = 1
	for r1, m1 in zip(r, m):
		r1 %= m1
		if m0 < m1:
			r0, r1 = r1, r0
			m0, m1 = m1, m0
		if m0 % m1 == 0:
			if r0 % m1 != r1:
				return (0, 0)
			continue
		g, im = inv_gcd(m0, m1)
		u1 = m1 // g
		if (r1 - r0) % g:
			return (0, 0)
		x = (r1 - r0) // g % u1 * im % u1
		r0 += x * m0
		m0 *= u1
		if r0 < 0:r0 += m0
	return (r0, m0)


n = int(input())
e = int(input())
# x^2 + y 5^e - n = 0 has integer solution ?
# e = 0 -> ok.
if e == 0 or n == 0:
	print(0)
	exit()

def floorsqrt(n):
	# only for n <= 10 ** 18
	ok = 10 ** 9 + 10
	ng = 0
	while ok - ng > 1:
		t = (ok + ng) // 2
		if t * t > n: ok = t
		else: ng = t
	return ng

if (n % (5 ** e) == 0):
	print(0)
	exit()

ee = e
nn = n
basis = 1
while n % 25 == 0:
	n //= 25
	e -= 2
	basis *= 5

if e == 0:
	print(0)
	exit()

if not (n % 5 == 1 or n % 5 == 4):
	print("NaN")
	exit()

a = -1
for i in range(5):
	if (i * i - n) % 5 == 0:
		a = i
		break

assert a >= 0

for t in range(2, e+1):
	c = (a * a - n) // (5 ** (t-1))
	y = -1
	for yy in range(5):
		if (2 * a * yy + c) % 5 == 0:
			y = yy
			break
	assert y >= 0
	b = (a + 5 ** (t-1) * y) % (5 ** t)
	a = b

a *= basis
a %= (5 ** ee)
if a > 2 ** 29:
	a -= 5 ** ee

print(a)
#print((a * a - nn) % (5 ** ee) == 0)