#include<cstdio>
typedef long long ll;

ll palindrome1(ll x){
	int cnt = 0;
	ll y = x;
	ll z = 0;
	while(x>0){
		z *= 10;
		z += x % 10;
		x /= 10;
		cnt++;
	}
	for(int i=0;i<cnt;i++) y *= 10;
	return y + z;
}

ll palindrome2(ll x){
	int cnt = 0;
	ll y = x;
	ll z = 0;
	while(x>0){
		z *= 10;
		z += x % 10;
		x /= 10;
		cnt++;
	}
	y /= 10;
	for(int i=0;i<cnt;i++) y *= 10;
	return y + z;
}

int main(){
	ll n;
	int ans = 0;
	scanf("%lld",&n);
	n /= 1000000001;
	for(int i=1;i<100000;i++){
		if(palindrome1(i)<=n) ans++;
		if(palindrome2(i)<=n) ans++;
	}
	printf("%d\n",ans);
}