#include<iostream>
using namespace std;
int main(){
    long long N,ans=0;
    long long tmp,num,reverse;
    int k,l;
    cin >> N;
    N /= 1e9+1;
    for(int i=1;i<=N;i++){
        num = i;
        reverse = 0;
        while(num > 0){
            tmp = num%10;
            reverse = reverse*10+tmp;
            num /= 10;
        }
        if(reverse == i) ans++;
    }
    cout << ans << endl;
    return 0;
}