#include <bits/stdc++.h>

#define REP(i,a,b) for(int i=a;i<b;++i)
#define rep(i,n) for(int i=0;i<n;++i)
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
#define ALL(a) begin(a),end(a)
#define ifnot(a) if(not (a))
#define dump(x)  cerr << #x << " = " << (x) << endl
using namespace std;

int dx[] = { 0,1,0,-1 };
int dy[] = { 1,0,-1,0 };
#define INF (1 << 28)
ull mod = (int)1e9 + 7;
//.....................
const int MAX = (int)1e5 + 5;

int T = 1;
int N;
vector<int> a;

static int prime[MAX + 5];
static int isprime[MAX + 5];
void eratosthenes(int N) {
        for (int i = 0; i < N; i++) {
                isprime[i] = 1;
        }
        for (int i = 2; i < sqrt((double)N); i++) {
                if (isprime[i]) {
                        for (int j = 0; i * (j + 2) < N; j++) {
                                isprime[i *(j + 2)] = 0;
                        }
                }
        }
        int a = 0;
        for (int i = 2; i < N; i++) {
                if (isprime[i]) {
                        prime[a++] = i;
                }
        }
}

void solve() {
        eratosthenes(MAX);
        cin >> N;
        // rep(i, 100) {
        //      cout << prime[i] << endl;
        // }
        int dp[20005] = {1, 0, 0};
        for (int i = 0; prime[i] <= N; i++) {
                for (int j = N; ; j--) {
                        int a = j - prime[i];
                        if (a < 0) break;
                        if (dp[a] > 0) if (dp[j] < dp[a] + 1) dp[j] = dp[a] + 1;
                }
        }
        if (dp[N] == 1) cout << -1 << endl;
        else cout << dp[N] - 1 << endl;
}

signed main() {
  cout << fixed << setprecision(20);
  rep(i, T) solve();
  return 0;
}