#include <bits/stdc++.h>

using namespace std;

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

typedef long long ll;

const int MOD = 1000000007;
const int INF = 1001001001;
vector<bool> prime(22222 , true);

void pre_calc() {
    for (int i = 2; i < 22222; i++) {
        for (int j = 2; j * i < 22222; j++) {
            prime[i * j] = false;
        }
    }
    return;
}

int main () {
    int n;
    cin >> n;
    pre_calc();
    vector<int> dp(n + 1 , 0);
    //dp[n] = 1;
    for (int i = 2; i <= n; i++) {
        if (prime[i] == false)continue;
        vector<int> dp2;
        dp2 = dp;
        for (int j = n; j >= 0; j--) {
            //if (prime[j - i] == false) continue;
            if(j - i >= 0 && (dp[j] > 0 || j == n)) dp2[j - i] = max(dp2[j - i] , dp[j] + 1);
        }
        dp = dp2;
    }
    int ans = dp[0];
    if (dp[0] == 0) ans = -1;
    cout << ans << endl;
    /*
    for (int i = 0; i <= n; i++) {
        cout << i << " : " << dp[i] << endl;
    }
    */
    return 0;
}