import itertools

N = input()

if (N < 10**9):
    print 0
    exit()

ans = 0

for p in itertools.product('0123456789', repeat=5):
    p = int(''.join(p))
    q = str(p)[::-1]
    if len(str(p)) % 2 == 1:
        q = q[1:]
    nnn = int(str(p) + str(q))
    nnn = nnn*10**9 + nnn
    if int(nnn) <= N:
        ans += 1

print max(0, ans-1)