#include <bits/stdc++.h>
using namespace std;

typedef long long   signed int LL;
typedef long long unsigned int LU;

#define incID(i, l, r) for(int i = (l)    ; i <  (r); i++)
#define incII(i, l, r) for(int i = (l)    ; i <= (r); i++)
#define decID(i, l, r) for(int i = (r) - 1; i >= (l); i--)
#define decII(i, l, r) for(int i = (r)    ; i >= (l); i--)
#define  inc(i, n) incID(i, 0, n)
#define inc1(i, n) incII(i, 1, n)
#define  dec(i, n) decID(i, 0, n)
#define dec1(i, n) decII(i, 1, n)

#define inII(v, l, r) ((l) <= (v) && (v) <= (r))
#define inID(v, l, r) ((l) <= (v) && (v) <  (r))

#define PB push_back
#define EB emplace_back
#define MP make_pair
#define FI first
#define SE second
#define UB upper_bound
#define LB lower_bound
#define PQ priority_queue

#define  ALL(v)  v.begin(),  v.end()
#define RALL(v) v.rbegin(), v.rend()
#define  FOR(it, v) for(auto it =  v.begin(); it !=  v.end(); ++it)
#define RFOR(it, v) for(auto it = v.rbegin(); it != v.rend(); ++it)

template<typename T> bool   setmin(T & a, T b) { if(b <  a) { a = b; return true; } else { return false; } }
template<typename T> bool   setmax(T & a, T b) { if(b >  a) { a = b; return true; } else { return false; } }
template<typename T> bool setmineq(T & a, T b) { if(b <= a) { a = b; return true; } else { return false; } }
template<typename T> bool setmaxeq(T & a, T b) { if(b >= a) { a = b; return true; } else { return false; } }
template<typename T> T gcd(T a, T b) { return (b == 0 ? a : gcd(b, a % b)); }
template<typename T> T lcm(T a, T b) { return a / gcd(a, b) * b; }

// ---- ----

LL ex(LL x, LL y) {
	return (y == 0 ? 1 : x * ex(x, y - 1));
}

LL dig(LL x, LL y) {
	return (x / ex(10, y)) % 10;
}

LL len(LL x) {
	LL c = 0;
	while(x) { x /= 10; c++; }
	return c;
}

int main() {
	LL n;
	cin >> n;
	
	LL ans = 0;
	incID(i, 1, 10000) {
		LL c = len(i);
		
		LL a = 0;
		inc(j, c) { a *= 10; a += dig(i, j); }
		a += i * ex(10, c);
		a *= 1000000001;
		
		if(a <= n) { ans++; }
	}
	
	incID(i, 1, 100000) {
		LL c = len(i);
		
		LL a = 0;
		incID(j, 1, c) { a *= 10; a += dig(i, j); }
		a += i * ex(10, c - 1);
		a *= 1000000001;
		
		if(a <= n) { ans++; }
	}
	
	cout << ans << endl;
	
	return 0;
}