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

using ll = int_fast64_t;
#define rep(i,n) for(int i=0;i<(n);++i)

signed main(){

  ll n;
  cin>>n;

  ll ans = 0;
  auto dfs =[&](auto&&dfs,ll x)->void{
    if(100<=x and x<=n)ans++;
    if(x>n)return;
    if(x!=0)dfs(dfs,x*10);
    dfs(dfs,x*10+3);
    dfs(dfs,x*10+6);
    dfs(dfs,x*10+9);
  };
  dfs(dfs,0);

  for(int i=10;i<=min<ll>(n,100);++i){
    if(i%3==0)ans++;
  }
  cout<<(ans)<<endl;

}