#define  _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <algorithm>
#include <utility>
#include <functional>
#include <cstring>
#include <queue>
#include <stack>
#include <math.h>
#include <iterator>
#include <vector>
#include <string>
#include <set>
#include <math.h>
#include <iostream> 
#include<map>
#include <iomanip>
#include <stdlib.h>
#include <list>
#include <typeinfo>
#include <list>
#include <set>
using namespace std;
#define MAX_MOD 1000000007
#define REP(i,n) for(long long i = 0;i < n;++i)
#define LONG_INF 100000000000000
vector<int> sosuu;
int wow[3000][40001] = {};
void setted() {
	for (int i = 2;i <= 20000;++i) {
		for (int q = 2;q <= sqrt(i);++q) {
			if (i%q == 0) goto fail;
		}
		sosuu.push_back(i);
	fail:;
	}
}
int main() {
	int m;
	cin >> m;
	setted();
	for (int i = 1;i-1< sosuu.size();++i) {
		wow[i][sosuu[i - 1]] = max(1,wow[i][sosuu[i-1]]);
		for (int q = 0;q <= m;++q) {
			wow[i][q] = max(wow[i][q], wow[i - 1][q]);
			if (wow[i - 1][q] != 0&&q+sosuu[i-1] <= m) {
				wow[i][q + sosuu[i - 1]] = max(wow[i][q + sosuu[i - 1]], wow[i-1][q] + 1);
			}
		}
	}
	if (wow[sosuu.size()][m] == 0) {
		cout << -1 << endl;
		return 0;
	}
	cout << wow[sosuu.size()][m] << endl;
	return 0;
}