def c_number(N):
	n=0
	for i in range(len(N)):
		n+=N[i]*(10**i)
	return n
def gcd(a, b):
	while b:
		a, b = b, a % b
	return a
N=list(map(int,list(input())))
if len(N) == 2:
	print(gcd(c_number(N), c_number(N[::-1]))); exit()
n=set(N)
if len(n)==1: print(c_number(N)); exit()
if len(n)==2 and N.count(0)==len(N)-1:
	print(c_number(sorted(N,reverse=True)));exit()
if len(N)-N.count(0) == 2:
	n=list(n-{0})
	print(gcd(c_number([n[0],n[1]]), c_number([n[1],n[0]])));exit()
s=c_number(N)
if s//9 != s/9:
	if s//3 != s/3:
		print(1);exit()
	else:
		print(3);exit()
min_diff=10
for i in n:
	for j in n-{i}:
		if max(i-j,j-i)<min_diff:
			min_diff = max(i-j,j-1)
			s=(i,j)

print((max(i,j)-min(i,j))*9)