#include<bits/stdc++.h>
using namespace std;
int hws(int n)
{
	int t=0;
	while(n!=0)
	{
		t=t*10+n%10;
		n=n/10;
	}
		return t;
}
int main()
{
	int n;
	cin>>n;
	int cnt=0;
	for(int i=1;i<=n;i++)
	{
		if(hws(i)==i)
		{
		    cnt++;	
		}
	}
	cout<<cnt<<endl;
	return 0;
}
/**************************************************************
	Problem: 1149
	User: chenkexin
	Language: C++
	Result: Accepted
	Time:16 ms
	Memory:2072 kb
****************************************************************/