#include <cstdio>
#include <iostream>
#include <string>
#include <vector>
#include <sstream>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <typeinfo>
#include <numeric>
#include <functional>
#include <unordered_map>
#include <bitset>
#include <stack>


using namespace std;
using ll = long long;
using ull = unsigned long long;

const ll INF = 1e16;
const ll MOD = 1e9 + 7;

#define REP(i, n) for(ll i = 0; i < n; i++)




int main() {
    ll n;
    cin >> n;
    vector<bool> flag(n + 1, true);
    vector<ll> sosu;
    for(ll i = 2; i <= n; i++){
        if(flag[i]){
            sosu.push_back(i);
            for(ll j = i; j <= n; j += i){
                flag[j] = false;
            }
        }
    }
    
    vector<vector<ll>> dp(sosu.size() + 1, vector<ll>(n + 1, -INF));
    dp[0][0] = 0;
    for(ll i = 0; i < sosu.size(); i++){
        for(ll j = 0; j <= n; j++){
            if(dp[i][j] >= 0){
                if(j + sosu[i] <= n){
                    dp[i + 1][j + sosu[i]] = max(dp[i + 1][j + sosu[i]], dp[i][j] + 1);
                }
                dp[i + 1][j] = max(dp[i + 1][j], dp[i][j]);
            }
        }
    }
    if(dp[sosu.size()][n] >= 1) cout << dp[sosu.size()][n] << endl;
    else cout << -1 << endl;
}