#include<iostream>
#include<cstdio>
using namespace std;
int huiwen(int m)
{
	int sum=0,a=m;
	while(m)
	{
		sum=sum*10+m%10;
		m/=10; 
	}
	if(sum==a)
	return 1;
	else
	return 0;
}
int main()
{
int x,m,sum=0;
cin>>x;
for(m=1;m<=x;m++)
{
	if(huiwen(m))
	{
	sum++;	
	}
}
cout<<sum;
}