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

#define fi first
#define se second
#define repl(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define rep(i,n) repl(i,0,n)
#define each(itr,v) for(auto itr:v)
#define pb(s) push_back(s)
#define mp(a,b) make_pair(a,b)
#define all(x) (x).begin(),(x).end()
#define dbg(x) cout<<#x"="<<x<<endl
#define maxch(x,y) x=max(x,y)
#define minch(x,y) x=min(x,y)
#define uni(x) x.erase(unique(all(x)),x.end())
#define exist(x,y) (find(all(x),y)!=x.end())
#define bcnt(x) bitset<32>(x).count()

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> P;
typedef pair<P, int> PPI;
typedef pair<ll, ll> PL;
typedef pair<P, ll> PPL;

#define INF INT_MAX/3

#define MAX_N 1000

ll rec(ll n,ll nd,ll digit,bool flag){
  if(nd>digit/2+digit%2)return 1;
  ll res=1;
  ll maxd=(n/(ll)pow(10,digit-nd))%10;
  if(flag)res*=maxd;
  else res*=digit==1?9:10;
  return res*rec(n,nd+1,digit,flag);
}

ll n;
ll res=0;

int main(){
	cin.sync_with_stdio(false);
  cin>>n;
  n/=1000000001;
  ll digit=1;
  for(ll x=1;x<=n;x*=10){
    res+=rec(min(x*10-1,n),1LL,digit++,x*10-1>=n);
  }
  cout<<res<<endl;
	return 0;
}