#include<bits/stdc++.h>
using namespace std;
int huiwen(int n){
    int t=0;
    while(n!=0)
    {
        t=t*10+n%10;
        n=n/10;
    }
    return t;
}
int main()
{
    int n;
    int s=0;
    cin>>n;
    for(int i=1;i<=n;i++)
    {
        if(huiwen(i)==i){
            s+=1;
        }
    }
    cout<<s;
    return 0;
}
/**************************************************************
	Problem: 1149
	User: luyanchen
	Language: C++
	Result: Accepted
	Time:18 ms
	Memory:2072 kb
****************************************************************/