#include <iostream>
#include <string>
#include <algorithm>

int main() {
    std::string n;
    std::cin >> n;
    while (n.length() < 18) {
        n = "0" + n;
    }
    if (n.length() == 19) {
        n = std::string(18, '9');
    }
    
    std::string S = n.substr(0, 9);
    std::string T = n.substr(9, 9);
    long long S_num = std::stoll(S);
    long long T_num = std::stoll(T);
    
    long long num;
    if (T_num >= S_num) {
        num = S_num;
    } else {
        num = S_num - 1;
    }
    
    long long ans = std::min(num, 9LL);
    long long x = 1;
    
    while (true) {
        bool br = false;
        for (long long i = x; i < 10 * x; ++i) {
            std::string i_str = std::to_string(i);
            std::string z = i_str + std::string(i_str.rbegin(), i_str.rend());
            if (std::stoll(z) <= num) {
                ans += 1;
            } else {
                br = true;
            }
            for (int j = 0; j < 10; ++j) {
                std::string z_with_j = i_str + std::to_string(j) + std::string(i_str.rbegin(), i_str.rend());
                if (std::stoll(z_with_j) <= num) {
                    ans += 1;
                } else {
                    br = true;
                }
            }
        }
        x *= 10;
        if (br) {
            break;
        }
    }
    
    std::cout << ans << std::endl;
    return 0;
}