#include <iostream>
#include <cmath>

using namespace std;
bool sushu(int n){
	int i;
	bool f=true;
	for(i=2;i<=sqrt(n);i++){
		if(n%i==0){
			f=false;
			break;
		}
	}
	if(n<=1){
		f=false;
	}
	return f;
}
bool huiwen(int n){
	bool f=false;
	int g=n%10,s=n/10%10,b=n/100%10,q=n/1000%10,w=n/10000;
	if(n<=99&&g==s||n<=9){
		f=true;
	}
	else if(n>99&&n<=999&&g==b){
		f=true;
	}
	else if(n>999&&n<=9999&&g==q&&s==b){
		f=true;
	}
	else if(n>=10000&&g==w&&s==q){
		f=true;
	}
	return f;
	
}
int main(){
	int n,i,c=0;
	cin>>n;
	for(i=1;i<=n;i++){
		if(huiwen(i)==true){
			c++;
		}
	}
	cout<<c<<endl;
}
/**************************************************************
	Problem: 1149
	User: admin
	Language: C++
	Result: Accepted
	Time:17 ms
	Memory:2072 kb
****************************************************************/