#pragma GCC target("avx2")
#pragma GCC optimize("03")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std; typedef long double ld; typedef long long ll;
typedef unsigned long long ull;
#define endl "\n"
#define FOR(i,a,b) for(int i=(a);i<=(b);i++)
#define rep(i,n) for(int i=0;i<(n);i++)
#define PII pair<int, int>
#define PLL pair<ll, ll>
#define ALL(x) (x).begin(), (x).end()
constexpr int INF=1<<30; constexpr ll LINF=1LL<<60; constexpr ll mod=1e9+7; constexpr int NIL = -1;
template<class T>vector<T> vec(int len, T elem) { return vector<T>(len, elem); } // auto dp = vec(52, vec(103, vec(103, INF)));
template<class T>inline bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T>inline bool chmin(T &a, const T &b) { if (b<a) { a = b; return 1; } return 0; }
template<class T>inline int popcount(T a) {return __builtin_popcount(a);}
template<class T>inline T emod(T a, T p) { return (a%p + p) % p;}
//-------------------
constexpr ll K = 1e9+1;
int main() {
    cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(15);
    ll n; cin >> n;
    ll m = n/K;
    ll ans = 0;
    for(ll i = 1; i<100000; i++) {
        auto s = to_string(i);
        string S = s, T = s;
        reverse(ALL(s));
        S += s;
        T += s.substr(1, s.size()-1);
        if(stoll(S) <= m) ans++;
        if(stoll(T) <= m) ans++;
    }
    cout << ans << endl;
    return 0;
}