#include<bits/stdc++.h>
using namespace std;
using uint = unsigned int;
using ll = long long;
using ull = unsigned long long;
template<class T> using V = vector<T>;
template<class T> using VV = V<V<T>>;
template<class T> using VVV = V<VV<T>>;
template<class T> using VVVV = VV<VV<T>>;
#define rep(i,n) for(ll i=0ll;i<n;i++)
#define REP(i,a,n) for(ll i=a;i<n;i++)
const long long INF = (1LL << 60);
const long long mod99 = 998244353;
const long long mod107 = 1000000007;
const long long mod = mod99;
#define eb emplace_back
#define pb eb
#define be(v) (v).begin(),(v).end()
#define all(i,v) for(auto& i : v)
#define all2(i,j,v) for(auto& [i,j] : v)
template<class T, class U> void chmin(T& t, const U& u) { if (t > u) t = u; }
template<class T, class U> void chmax(T& t, const U& u) { if (t < u) t = u; }

// cin.tie(nullptr);
// ios::sync_with_stdio(false);
// cout << fixed << setprecision(20);

bool prime(ll n){
	if(n<=1) return 0;
	if(n==2) return 1;
	for(ll i=3;i*i<=n;i+=2) if(n%i==0) return 0;
	return 1;
}

void solve(){
  ll n;
  cin >> n;
  V<ll> dp(20010, INF);
  dp[0] = 0;
  REP(i,2,20001) if(prime(i)){
  	for(ll j=n;j>=i;j--) chmin(dp[j], dp[j-i]+1);
  }
  if(dp[n] == INF) dp[n] = -1;
  cout << dp[n] << endl;
}





int main(){
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  int t=1;
  // cin >> t;
  rep(i,t) solve();
}