#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MOD = 1000000007;
const int MAX_N = 20010;

#define REP(i,n) for((i)=0;(i)<(int)(n);(i)++)

vector<int> p;
bool prime[MAX_N];
int dp[MAX_N];

void primeList(){
    fill(prime + 2, prime + MAX_N, true);
    for (int i = 2; i < MAX_N; i++){
        if (prime[i]){
            for (int j = 2 * i; j < MAX_N; j += i){
                prime[j] = false;
            }
        }
    }
}

int main(){
    primeList();
    int n, i, j;
    cin >> n;
    REP(i, n + 1){
        if (prime[i]) p.push_back(i);
    }

    REP(i, MAX_N) dp[i] = -1;
    dp[0] = 0;
    for (int i = 0; i < p.size(); i++){
        for (int j = n; j >= 0; j--){
            if (j < p[i] || dp[j - p[i]] == -1) continue;
            else dp[j] = max(dp[j], dp[j - p[i]] + 1);
        }
    }

    cout << dp[n] << endl;

    return 0;
}