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

    using namespace std;
    map <int, int> m;
    int main(){
        int n;
        cin >> n;
        int cnt = 0;
        for (int i = 0;i < n ; ++i) {
            string d = to_string ( i);
            //cout << d << endl;
            reverse(d.begin (), d.end());
            //cout << d << endl;
            int sum  = 0, f = 1;
            for (int i = d.size() - 1 ; i >= 0; -- i){
                sum += (d[i] - '0') * f;
                f *=10;
                //cout << sum << " ";
            }
            // << endl;

            //cout << d << " ";
            //cout << sum << "___"  << endl;
            if ((sum + i ) == n) {
                cnt ++;
            }
        }
        cout << cnt << endl;
        return 0;
}