Untitled

#include <bits/stdc++.h>

using namespace std;

int max_digit(long long a, int digit)
{
 if(a == ???) return ???;
  else return max_digit(a / ???, max(digit, (int)(a % ???)));
}

int main()
{
 long long a;
 cin >> a;
 cout << max_digit(a, 0);
}