#include <bits/stdc++.h>

using namespace std;

#define INF 2000000000
//#define MOD 1000000007
#define X 1000000001
typedef long long ll;
typedef pair<int, int> P;

bool p(string s){
	int size = s.size();
	int l = 0;
	int r = size-1;
	while (true) {
		if (l>=r) {
			break;
		}
		if (s[l]!=s[r]) {
			return false;
		}
		l++; r--;
	}
	return true;

}

int main()
{
	ll n;
	cin >> n;

	ll x = X;
	int ret=0;
	while (true) {
		if (x>n) {
			break;
		} else {
			string s = to_string(x);
			if (p(s)) ret++;
		}
		x += X;
	}
	cout << ret << endl;
}