#include <bits/stdc++.h>
using namespace std;
int n,h;
int hw(int s){
	int ys=0;
	while(s!=0){
		ys=ys*10+s%10;
		s=s/10;
	}
	return ys;
} 
int main(){
	cin>>n;
	for(int i=1;i<=n;i++){
		if(i==hw(i)){
			h++;
		}
	}
	cout<<h;
	
}


/**************************************************************
	Problem: 1149
	User: 15159808820
	Language: C++
	Result: Accepted
	Time:14 ms
	Memory:2072 kb
****************************************************************/