include

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;

}