#include <bits/stdc++.h>  

using namespace std;

#define FOR(i, j, k) for(int i = j; i < k; ++i)
#define rep(i, j) FOR(i, 0, j)
#define repr(i, j) for(int i = j; i >= 0; --i)
#define INF (1 << 30)
#define MOD 1e9 + 7

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> P;

int main() {
	ll N;
	scanf("%lld", &N);
	ll M = N / (1e9 + 1);
	int ans;
	ll tmp = 1e9 + 1;
	rep(i, M) {
		string num = to_string(tmp);
		bool flag = false;
		rep(i, num.size()/2) {
			if(num[i] == num[num.size() - i]) flag = true;
			else {
				break;
				flag = false;
			}
		}
		if(flag) ++ans;
	}
	printf("%lld\n", ans);
	return 0;
}