#include<bits/stdc++.h>
#define rep(i, n) for(int i = 0; i < (int)(n); i++)
using namespace std;
typedef long long ll;
int INF = (1LL << 30) - 1;
ll num = 1000000001;
int MOD = 1e9+7;
string to_str(ll A){
    stringstream ss;
    ss << A;
    return ss.str();
}
main(){
    ll N,cnt = 0;
    cin >> N;
    for(ll i = num;i <= N;i += num){
        string S = to_str(i);
        bool flag = 1;
        rep(j,S.size()/2){
            flag &= (S[j] == S[S.size() - j - 1]);
        }
        if(flag)cnt++;
    }
    cout << cnt << endl;
}