#include <algorithm>
#include <iostream>
#include <vector>
#include <string>
#include <climits> // FOO_MAX, FOO_MIN
#include <cmath> 
#include <cstdlib> // abs(int)
#include <numeric>

#define roundup(n,d) ( ((n) + ((d)-1)) / (d) )
#define ll long long
#define assign_max(into, compared) (into = max((into), (compared)))
#define assign_min(into, compared) (into = min((into), (compared)))

using namespace std;

bool is_prime(int n){
    if (n <= 1) return false;
    if (n == 2) return true;
    if (n % 2 == 0) return false;
    const int limit = min(((int)sqrt(n))+1,n);
    for(int i = 3;i <= limit;i+=2){
        if (n % i == 0){
            return false;
        }
    }
    return true;
}
//[2,limit]
vector<int> primenumbers(int limit){
    vector<int> primes;
    for(int i = 2;i <= limit;i++){
        if(is_prime(i)){
            primes.push_back(i);
        }
    }
    return primes;
}


int main(void){
    int n;
    cin >> n;
    auto primes = primenumbers(n);
    const int primes_n = primes.size();
    vector<vector<int>> dp (primes_n+1, vector<int> (n+1));
    for(int i = 0;i < primes_n;i++){
        for(int j = 0;j <= n;j++){
            dp[i+1][j] = dp[i][j];
            if(j-primes[i] < 0){
                continue;
            }

            if(dp[i][j-primes[i]] == 0 && j-primes[i] != 0){
                continue;
            }

            dp[i+1][j] = max(dp[i][j], dp[i][j-primes[i]]+1); 
        }
    }

    int ans = dp[primes_n][n] > 0 ? dp[primes_n][n] : -1;
    
    /* for(auto &v : dp){
        for(auto &i : v){
            cout << i << " ";
        }
        cout << endl;
    } */
    cout << ans << endl;
}