def is_palindrome(x):
    s = str(x)
    l = len(s)
    if s[:l//2] == s[::-1][:l//2]:
        return True
    else:
        return False

N = int(input())
M = 10**9+1

ans = 0
for i in range(1, 10**5):
    if is_palindrome(i) and M*i <= N:
        ans += 1

print(ans)