#include <iostream>
#include <string>
#include <map>
#include <vector>
#include <algorithm>
#include <queue>
#include <stack>
#include <cstdio>
#include <cmath>

using namespace std;

#define REP(i,k,n) for(int i=k;i<n;i++)
#define rep(i,n) for(int i=0;i<n;i++)
#define EPS 1e-14

#define all(v) v.begin(),v.end()
#define INF 1<<30
#define mp make_pair
#define pb push_back

#define fi first
#define se second

#define each(it,c) for(auto it=(c).begin();it!=(c).end();it++)

typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,int> pii;

typedef long long ll;

bool prime[20001]; 
void makeprime(){
	rep(i,20000) prime[i] = true;
	prime[0] = false;
	prime[1] = false;
	REP(i,2,sqrt(20000)+1){
		if(prime[i]==true){
			REP(j,2,sqrt(20000)+1){
				if(i*j<=20000) prime[i*j] = false;
			}
		}
	}
	return;
}

void solve(){
	int N;
	cin >> N;
	int dp[20001];
	rep(i,20001) dp[i] = -1;
	dp[0] = 0;
	REP(i,2,N+1){
		if(prime[i]==true){
			for(int j=i*i;j>=i;j--){
				if(j<=20000 && dp[j-i]>=0){
					dp[j] = max(dp[j],dp[j-i]+1);
				}
				// cout  <<j << " : " << dp[j] << "  ";
			}
			// cout << endl;
		}
	}

	cout << dp[N] << endl;
}

int main(){
	makeprime();
	solve();
	return 0;
}