#include <iostream>
#include <string>
#define int long long
using namespace std;

int high;

string reverse(string s) {
	string ret;
	for (int i = (int)s.length() - 1; i >= 0; i--) ret += s[i];
	return ret;
}

bool check(string s) {
	//0文字目は最下位桁
	if (s.length() == 0 || s[s.length() - 1] == '0') return false;
	
	int value = 0;
	int mul = 1;
	for (int i = 0; i < s.length(); i++) {
		value += (s[i] - '0') * mul;
		mul *= 10;
	}
	if (1 <= value && value <= high) return true;
	return false;
}

int dfs(string s) {
	if (s.length() > 4) return 0;
	
	int ret = 0;
	
	if (check(s + reverse(s))) ret++;
	for (char i = '0'; i <= '9'; i++) {
		if (check(s + i + reverse(s))) ret++;
	}
	
	for (char i = '0'; i <= '9'; i++) {
		ret += dfs(s + i);
	}
	return ret;
}

signed main() {
	int n;
	cin >> n;
	
	high = n / 1000000001;
	cout << dfs("") << endl;	//1以上high以下の回文がいくつあるか？
	return 0;
}