#include <bits/stdc++.h>
using namespace std;
#define FOR(i, n) for(int i = 0; i < (n); i++)
#define MEM(a, x) memset(a, x, sizeof(a))
#define ALL(a) a.begin(), a.end()
#define UNIQUE(a) a.erase(unique(ALL(a)), a.end())
typedef long long ll;

int n, dp[2300][20005];

bool isPrime(int x) {
	if (x < 2) return false;
	for (int i = 2; i * i <= x; i++) {
		if (x % i == 0) return false;
	}
	return true;
}

vector<int> getPrimes(int n) {
	vector<int> ret;
	for (int i = 2; i <= n; i++) {
		if (isPrime(i)) ret.push_back(i);
	}
	return ret;
}

int main(int argc, char const *argv[]) {
	ios_base::sync_with_stdio(false);
	cin >> n;
	// FOR(i, 2300) {
	// 	FOR(j, 20005) dp[i][j] = -1;
	// }
	vector<int> p = getPrimes(n);
	for (int i = 0; i < p.size(); i++) {
		dp[i+1][p[i]] = 1;
		FOR(j, n+1) {
			// if (j-p[i] == 0) dp[i+1][j] = 1;
			if (j-p[i] >= 0 && dp[i][j-p[i]] >= 0 && j-p[i] != p[i] && j-p[i] != 1) {
				dp[i+1][j] = max({dp[i+1][j], dp[i][j], dp[i][j-p[i]]+1});
			}
			else dp[i+1][j] = max(dp[i+1][j], dp[i][j]);
		}
	}
	// FOR(i, n+1) cout << dp[p.size()][i] << " ";
	// cout << endl;
	cout << (dp[p.size()][n] == 0 ? -1 : dp[p.size()][n]) << endl;
	return 0;
}