/*
    Author:zeke
    
    pass System Test!
    GET AC!!
*/
#include <iostream>
#include <queue>
#include <vector>
#include <iostream>
#include <vector>
#include <string>
#include <cassert>
#include <algorithm>
#include <functional>
#include <cmath>
#include <queue>
#include <set>
#include <stack>
#include <deque>
#include <map>
#include <iomanip>
#include <utility>
#include <stack>
using ll = long long;
using ld = long double;
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define all(x) (x).begin(), (x).end()
#define rep3(var, min, max) for (ll(var) = (min); (var) < (max); ++(var))
#define repi3(var, min, max) for (ll(var) = (max)-1; (var) + 1 > (min); --(var))
#define Mp(a, b) make_pair((a), (b))
#define F first
#define S second
#define Icin(s) \
    ll(s);      \
    cin >> (s);
#define Scin(s) \
    ll(s);      \
    cin >> (s);
template <class T>
bool chmax(T &a, const T &b)
{
    if (a < b)
    {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
bool chmin(T &a, const T &b)
{
    if (b < a)
    {
        a = b;
        return 1;
    }
    return 0;
}
typedef pair<ll, ll> P;
typedef vector<ll> V;
typedef vector<V> VV;
typedef vector<P> VP;
ll MOD = 1e9 + 7;
ll INF = 1e18;
const int N = pow(10, 5);

vector<bool> Isp(N + 1, true);

void sieve()
{
    Isp[0] = false;
    Isp[1] = false;
    for (int i = 2; pow(i, 2) <= N; i++)
    {
        if (Isp[i])
            for (int j = 2; i * j <= N; j++)
                Isp[i * j] = false;
    }
} //N以下の整数をふるってくれます
int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    sieve();
    V isp;
    rep(i,N+1)if(Isp[i])isp.push_back(i);
  //  cout<<isp[1]<<endl;
    ll n;
    cin >> n;
    VV dp(isp.size() + 10, V(n +10, -1));
    dp[0][0] = 0;
    rep(i,isp.size()){
        rep(j,n+1){
         //   cout<<i<<" "<<j<<endl;
            if(j>=1){
                if(dp[i][j]!=-1){
                    chmax(dp[i+1][j], dp[i][j]);
                }
            }
            if(j-isp[i]>=0){
                if(dp[i][j - isp[i]]!=-1){
                    chmax(dp[i+1][j], dp[i][j - isp[i]]+1);
                }
            }
          //  if(i+1==isp.size()&&j==n)cout<<dp[isp.size()][n]<<endl;
        }
    }
  //  cout<<dp[2][5]<<endl;
  if(dp[isp.size()][n]==1e18){
      cout<<-1<<endl;
      return 0;
  }
    cout << dp[isp.size()][n] << endl;
}