#include <bits/stdc++.h>
#define rep(i,n) for(int i=(0);i<(n);i++)

using namespace std;

typedef long long ll;

template<class T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1; } return 0; }

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);

	int n;
	cin >> n;

	vector<bool> isprime(20001, true);
	isprime[0] = false;
	isprime[1] = false;
	for(int i = 2; i <= 20000; i++){
		if(isprime[i]){
			for(int j = i + i; j <= 20000; j += i){
				isprime[j] = false;
			}
		}
	}

	vector<int> primes;
	rep(i, 20001) if(isprime[i]) primes.push_back(i);

	int m = primes.size();

	int dp[2][n+1];
	int INF = 1e8;
	rep(i, 2) rep(j, n+1) dp[i][j] = -1;
	dp[0][n] = 0;

	rep(i, m) {
		rep(j, n+1) dp[(i+1)%2][j] = -1;

		int p = primes[i];
		rep(j, n+1){
			chmax(dp[(i+1)%2][j], dp[i%2][j]);
			if(j-p >= 0 && dp[i%2][j] != -1) chmax(dp[(i+1)%2][j-p], dp[i%2][j] + 1);
		}
	}

	cout << dp[n%2][0] << endl;
}