#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include<math.h>
#define rep(i,a) for(int i=0;i<a;i++)
#define nrep(i,a,b) for(int i=a;i<b;i++)
#define mrep(i,a) for(int i=a;i>=0;i--)
#define ll long long
#define INF 11451419191810
using namespace std;

ll n;
vector<ll> p;

void dfs(ll sum, ll index,ll ans){
	if (index == p.size()) return;
	if (sum == n){
		cout << ans << endl;
		exit(0);
	}if (sum > n){
		return ;
	}
	else{
		nrep(i, index, p.size()){
			dfs(sum + p[index], i+1, ans + 1);
		}
	}
}

int main(){

	cin >> n;
	vector<bool> prime(n + 1);
	rep(i, n+1) prime[i] = true;
	prime[0] = false;
	prime[1] = false;
	ll index = 2;
	while (index*index < n){
		if (prime[index]){
			ll j = index + index;
			while (j <= n){
				prime[j] = false;
				j += index;
			}
		}index++;
	}ll count = 0;
	rep(i, n + 1) if (prime[i]) p.push_back(i);
	dfs(0, 0, 0);
	cout << -1 << endl;
	return 0;
}