import sys

def solve():
    n = int(input())

    n //= 10**9 + 1
    ans = 0

    for k in range(1, 10):
        if k & 1:
            for j in range(10):
                palis = []
                make_palindrome(1, k, str(j), palis)

                for p in palis:
                    ans += p <= n
        else:
            palis = []

            make_palindrome(0, k, '', palis)

            for p in palis:
                ans += p <= n

    ans -= 1
    
    print(ans)

def make_palindrome(i, n, s, a):
    if i == n:
        a.append(int(s))
        return
    elif n - i == 2:
        for j in range(1, 10):
            make_palindrome(i + 2, n, str(j) + s + str(j), a)
    else:
        for j in range(0, 10):
            make_palindrome(i + 2, n, str(j) + s + str(j), a)

if __name__ == '__main__':
    solve()