#include <bits/stdc++.h>
using namespace std;
template <class T>
inline T bigmod(T p, T e, T M) {
  T ret = 1;
  for (; e > 0; e >>= 1) {
    if (e & 1) ret = (ret * p) % M;
    p = (p * p) % M;
  }
  return (T)ret;
}
template <class T>
inline T gcd(T a, T b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
template <class T>
inline T modinverse(T a, T M) {
  return bigmod(a, M - 2, M);
}
template <class T>
inline T lcm(T a, T b) {
  a = abs(a);
  b = abs(b);
  return (a / gcd(a, b)) * b;
}
template <class T, class X>
inline bool getbit(T a, X i) {
  T t = 1;
  return ((a & (t << i)) > 0);
}
template <class T, class X>
inline T setbit(T a, X i) {
  T t = 1;
  return (a | (t << i));
}
template <class T, class X>
inline T resetbit(T a, X i) {
  T t = 1;
  return (a & (~(t << i)));
}
inline long long power(long long a, long long b) {
  long long multiply = 1;
  for (int i = (1); i <= (b); i++) {
    multiply *= a;
  }
  return multiply;
}
inline long long ABS(long long a) { return (a >= 0) ? a : -a; }
int main() {
  long long n;
  scanf("%lld", &n);
  if (n == 2) {
    printf("1\n");
    return 0;
  }
  if (n % 2 == 0) {
    printf("2\n");
    return 0;
  }
  bool flag = 0;
  for (long long i = 3; i * i <= n; i++) {
    if (n % i == 0) {
      flag = 1;
      break;
    }
  }
  if (flag == 0) {
    printf("1\n");
    return 0;
  }
  long long m = n - 2;
  flag = 0;
  for (long long i = 3; i * i <= m; i++) {
    if (m % i == 0) {
      flag = 1;
      break;
    }
  }
  if (flag == 0) {
    printf("2\n");
    return 0;
  }
  printf("3\n");
  return 0;
}
