#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define rrep(i,n) for(int i = 1; i <= (n); ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<P> vp;
#define dame { puts("-1"); return 0;}
#define yn {puts("Yes");}else{puts("No");}


/*
    Max_Prime以下の素数をprimes[]に格納
*/

const int Max_Prime = 21000;
vector<int> tmp_primes;
vector<int> primes;

void PrimeInit() {
    rep(i,Max_Prime)tmp_primes[i] = 1;
    tmp_primes[0] = 0;
    tmp_primes[1] = 0;

    rep(i,Max_Prime){
        if(tmp_primes[i] == 0)continue;
        int j = 2;
        while(i * j <= Max_Prime){
            tmp_primes[i*j] = 0;
            j++;
        }
    }
    
    rep(i,Max_Prime){
        if(tmp_primes[i])primes.push_back(i);
    }
}

int main(){
    PrimeInit();

    int dp[21000] = {};

    int i = 0;
    while(primes[i] <= 20000){
        int x = primes[i];
        srep(j,x,20001){
            dp[j] = max(dp[j], dp[j-x] + 1);
        }
        i++;
    }

    int n;
    cin >> n;

    if(dp[n] == 0)dp[n] = -1;
    cout << dp[n] << endl;
    return 0;
}