#define _USE_MATH_DEFINES
#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <complex>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
#include <iterator>
using namespace std;

int main()
{
    long long n;
    cin >> n;

    int ans = 0;
    for(int i=1; i<100000; ++i){
        string a = to_string(i);
        string b = a;
        reverse(b.begin(), b.end());

        for(int j=0; j<2; ++j){
            long long x = stoll(a + b.substr(j));
            x *= 1000000001;
            if(x <= n){
                string s = to_string(x);
                string t = s;
                reverse(t.begin(), t.end());
                if(s == t)
                    ++ ans;
            }
        }
    }
    cout << ans << endl;

    return 0;
}