#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
int main(){
	long long N;
	cin >> N;
	N /= 1000000001;
	int ans = 0;
	for (int i = 1; i < 100000; i++){
		string S = to_string(i);
		string T = S;
		reverse(T.begin(), T.end());
		string T2 = T.substr(1);
		if (stoll(S + T) <= N){
			ans++;
		}
		if (stoll(S + T2) <= N){
			ans++;
		}
	}
	cout << ans << endl;
}