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

#define rep(i,n) for(ll i = 0; i < n; i++) //[0,n)
#define srep(i,a,b) for(ll i = a; i < b; i++) //[a,b)
#define arep(i,a,b,d) for(ll 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 P = pair<ll,ll>;
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 = 1000000007;
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; }
ll mceil(ll a,ll b){ return (a+b-1)/b; }

int dp[3000][20202];
int main(void){
    int N; cin >> N;

    vector<int> isprime(20001,1);
    isprime[0] = isprime[1] = 0;

    srep(i,2,20000+1){
        if(!isprime[i]) continue;
        for(int j = 2*i; j <= 20000; j += i) isprime[j] = 0;
    }

    vector<int> pr;
    rep(i,20000+1) if(isprime[i]) pr.push_back(i);

    rep(i,2500) rep(j,20202) dp[i][j] = -1;

    int n = siz(pr);
    dp[0][0] = 0;
    rep(i,n){
        for(int j = N; j >= 0; j--){
            if(dp[i][j] == -1) continue;
            dp[i+1][j] = max(dp[i+1][j],dp[i][j]);
            dp[i+1][j+pr[i]] = max(dp[i+1][j+pr[i]],dp[i][j]+1);
        }
    }

    cout << (dp[n][N] <= 0 ? -1 : dp[n][N]);
}