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; }