#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define rep(i,n) FOR(i,0,n)
#define repr(i,n) for(int i=(n)-1;0<=i;--i)
#define each(e,v) for(auto&& e:(v))
#define DUMP(x) cerr<<#x<<": "<<(x)<<endl
#define DEBUG(x) cerr<<#x<<": "<<(x)<<" (L"<<__LINE__<<")"<<endl
using namespace std;
using vint = vector<int>;
using vdouble = vector<double>;
using vstring = vector<string>;
using ll = long long;
template <class T> void chmin(T& a, const T& b) { a = min(a, b); }
template <class T> void chmax(T& a, const T& b) { a = max(a, b); }

constexpr ll M = 1e9 + 1;

bool isPalindrome(string str) {
    const int s = str.size();
    rep(i, s/2) {
        if(str[i] != str[s-i-1]) return false;
    }
    return true;
}

int main() {
    ll n; cin >> n;
    int cnt = 0;
    for(ll a = M; a <= n; a += M) {
        if(isPalindrome(to_string(a))) cnt++;
    }
    cout << cnt << endl;
    return 0;
}