include <bits/stdc++.h>

using namespace std;

int main() {

int num, c, count = 0; cin >> num; for (int i = 1; i <= num; i++) {

int n = i, k = 0;
while (n != 0) {
	c = n % 10;
	k = k * 10 + c;
	n = n / 10;
}
if (k == i) {
	count++;
}

} cout << count; return 0; }