#include <bits/stdc++.h>

using namespace std;

#define FOR(i, j, k) for(int i = j; i < k; ++i)
#define rep(i, j) FOR(i, 0, j)
#define repr(i, j) for(int i = j; i >= 0; --i)
#define INF (1 << 30)
#define MOD 1e9 + 7

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> P;
template < typename T > string to_string( const T& n ){
	ostringstream stm;
	stm << n;
	return stm.str();
}

int main() {
	ll N;
	scanf("%lld", &N);
	N /= (1e9 + 1);
	ll ans = 0;
	FOR(i, 1, 1e5) {
		string num = to_string(i);
		string s = num, t = num;
		reverse(num.begin(), num.end());
		s = s + num;
		num += num.substr(1, num.size() - 1);
		if(stoll(s) <= N || stoll(t) <= N) ++ans;
	}
	printf("%lld\n", ans);
	return 0;
}