#define _CRT_SECURE_NO_WARNINGS
#include"bits/stdc++.h"
#define INF          1e9
#define INFLL        1e18
#define EPS          1e-9
#define MOD          1000000007
#define REP(i,n)     for(ll i=0,i##_len=(n);i<i##_len;++i)
#define REP1(i,n)    for(ll i=1,i##_len=(n);i<=i##_len;++i)
#define REPR(i,n)    for(ll i=(n)-1;i>=0;--i)
#define REPR1(i,n)   for(ll i=(n);i>0;--i)
#define REPC(i,obj)  for(auto i:obj)
#define ALL(obj)     (obj).begin(),(obj).end()
#define SETP(n)      cout<<fixed<<setprecision(n)
#define VV(T,h,w)    vector<vector<T>>(h,vector<T>(w))
#define VVI(T,h,w,i) vector<vector<T>>(h,vector<T>(w,i))
using namespace std;
using ll = long long;
template<typename T = ll>inline T in() { T ret; cin >> ret; return ret; }

int main()
{
    vector<bool>is_prime(20001, true); is_prime[0] = is_prime[1] = false;
    REP(i, 150) {
        if (is_prime[i]) {
            for (ll j = i * 2; j < 20001; j += i) {
                is_prime[j] = false;
            }
        }
    }
    vector<ll>prime;
    REP(i, 20001)if (is_prime[i])prime.push_back(i);
    //REPC(p, prime)cout << p << endl;

    ll n = in();
    auto dp = VVI(ll, prime.size() + 1, n + 1, -1);
    dp[0][0] = 0;
    REP(i, prime.size()) {
        REP(j, n + 1) {
            dp[i + 1][j] = max(dp[i + 1][j], dp[i][j]);
            if (j >= prime[i]) dp[i + 1][j] = max(dp[i + 1][j], dp[i][j - prime[i]] + 1);
        }
    }
    ll res = dp[prime.size()][n];
    cout << (res < 2 ? -1 : res) << endl;
}