//#include <bits/stdc++.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <iomanip>
#include <numeric>
#include <cmath>
#include <bit>
#include <cstdint>

#define rep(i,n) for(int i = 0; i < n; i++) //[0,n)
#define srep(i,a,b) for(int i = a; i < b; i++) //[a,b)
#define arep(i,a,b,d) for(int i = a; i < b; i += d)
#define all(A) (A).begin(),(A).end()
#define rall(A) (A).rbegin(),(A).rend()
#define pmt(A) next_permutation(all(A))
using namespace std;
using ll = long long;
using ull = unsigned long long;
using pq = priority_queue<ll,vector<ll>,greater<ll>>;
const ll inf = 1LL<<60;
const int iinf = (int)1e9+1;
const int mod9 = 998244353;
const int mod1 = (int)1e9+7;
struct Edge { int to; long long cost; int from; };
bool compe(const Edge &e,const Edge &e2){ return e.cost < e2.cost; }
using Graph = vector<vector<int>>;
using SGraph = vector<set<ll>>;
template <class T>
int siz(T& a){return (int)a.size();}
ll squa(ll a){ return a*a; }
double torad(double x){ return x*(acos(-1)/180.0); }
ll cross(ll ax,ll ay,ll bx,ll by){ return ax*by-ay*bx; }
ll mceil(ll a,ll b){ return (a+b-1)/b; }

int dp[20101];
int main(){
    int N; cin >> N;
    
    vector<int> isprime(N+1,1);
    isprime[0] = isprime[1] = 0;

    for(int p = 2; p <= N; p++){
        if(!isprime[p]) continue;
        for(int q = 2*p; q <= N; q += p) isprime[q] = 0;
    }

    vector<int> A; rep(i,N+1) if(isprime[i]) A.push_back(i);
    
    rep(i,2300) dp[i] = -1;

    dp[0] = 0;
    rep(i,siz(A)){
        for(int j = N; j >= 0; j--){
            if(A[i]+j <= N && dp[j] != -1) dp[A[i]+j] = max(dp[A[i]+j],dp[j]+1);
        }
    }

    cout << dp[N];
}