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