#include <bits/stdc++.h>
#define rep(i, a, n) for(int i = a; i < n; i++)
#define repb(i, a, b) for(int i = a; i >= b; i--)
#define all(a) a.begin(), a.end()
#define o(a) cout << a << endl
#define int long long
using namespace std;
typedef pair<int, int> P;

int prime[20010];
bool is_prime[20010];
int sieve(int n){
    int p = 0;
    for(int i = 0; i <= n; i++) is_prime[i] = true;
    is_prime[0] = is_prime[1] = false;
    for(int i = 2; i <= n; i++){
        if(is_prime[i]){
            prime[p++] = i;
            for(int j = 2*i; j <= n; j += i) is_prime[j] = false;
        }
    }
    return p;
}

int dp[20010];

signed main(){
    int n, sz;
    sz = sieve(20000);
    cin >> n;
    rep(i, 0, 20001){
        dp[i] = -1;
    }
    dp[0] = 0;
    rep(i, 0, sz){
        repb(j, 20000 - prime[i], 0){
            if(dp[j] == -1) continue;
            dp[j + prime[i]] = max(dp[j + prime[i]], dp[j] + 1);
        }
    }
    cout << dp[n] << endl;
}