#include<bits/stdc++.h>
using namespace std;
#define int long long

bool check(int a){
	string s = to_string(a);
	int len = s.length();
	bool ok = true;
	for(int i = 0; i < (len / 2) - 1; i++){
		if(s[i] != s[len - 1 - i]){
			ok = false;
			break;
		}
	}
	return ok;
}

signed main(){
	int a = 1e9 + 1;
	int n;
	cin >> n;
	int count = 0;
	for(int i = a; i < n; i += a){
		if(check(i)){
			count++;
		}
	}
	cout << count << endl;
}