#include <bits/stdc++.h>
using namespace std;
bool isprime(int n) {
  if (n < 2) return false;
  for (int i = 2; i * i <= n; i++)
    if (n % i == 0) return false;
  return true;
}
int main() {
  int n;
  cin >> n;
  if (isprime(n))
    cout << "1" << endl;
  else if (n % 2 == 0)
    cout << "2" << endl;
  else if (isprime(n - 2))
    cout << "2" << endl;
  else
    cout << "3" << endl;
  return 0;
}
