#include<stdio.h>
int huiWen(int x)
{
	int h=0,t=x;

	while(x>0){
		h=h*10+x%10;
		x/=10;
	}
	if(h==t){
		return 1;
	}else{
		return 0;
	}
}
int main()
{
	int n,i,c=0;
	scanf("%d",&n);
	for(i=1;i<=n;i++){
		if(huiWen(i)){
			c++;
		}
	}
	printf("%d",c);
	return 0;
}
/**************************************************************
	Problem: 1149
	User: admin
	Language: C
	Result: Accepted
	Time:21 ms
	Memory:1144 kb
****************************************************************/