n = int(input())
m = 10**9 + 1

ans = 0
for j in range(1, 10):
    if j * m <= n:
        ans += 1

for i in range(1, 10**4):
    si = str(i)
    si_r = si[::-1]
    if int(si + si_r) * m <= n:
        ans += 1
    for j in range(10):
        if int(si + str(j) + si_r) * m <= n:
            ans += 1

print(ans)