#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define endl '\n'
ll N = 1e9+7;
ll oo =1e13;
const ll maxx = 1000000 + 3;
ll n,k,q,x,y,z,l,r,mid,ans;


void go(ll num , set<ll>v) {
    if (num > n)return;
        ans++;
    for (ll j =0;j<10;j++) {
        set<ll>nv=v;
        nv.insert(j);
        if (nv.size()>2) {
            continue;
        }
        go(num*10+j,nv);
      
    }
}
void solve() {
    cin>>n;
    for (ll i =1 ;i <10;i++) {
        set<ll>v;

        v.insert(i);
        go(i,v);
        
    }
    cout<<ans<<endl;
}
int main() {
    ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    ll t=1 ;
    // cin >>t;
    while (t--) {
        ans=0;
        solve();
    }
}