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

	return 0;
}



/**************************************************************
	Problem: 1149
	User: zhuanghaoxiang
	Language: C++
	Result: Accepted
	Time:15 ms
	Memory:2072 kb
****************************************************************/