#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: linzihang
	Language: C++
	Result: Accepted
	Time:18 ms
	Memory:2072 kb
****************************************************************/