import itertools

N = input()
M = 10**9
a = N / M

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

ans = 0
s = str(a)
b = len(s)
keta = b/2+b%2

for p in itertools.product('0123456789', repeat=keta):
    orikaeshi = p[::-1]
    if len(p) % 2 == 1:
        orikaeshi = orikaeshi[1:]
    nnn = int(''.join(p) + ''.join(orikaeshi))
    nnn = nnn*10**9 + nnn
    if int(nnn) <= N:
        ans += 1

print max(0, ans-1)