#include<bits/stdc++.h>
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
#define pb push_back
int dy[]={0, 0, 1, -1, 1, 1, -1, -1};
int dx[]={1, -1, 0, 0, 1, -1, -1, 1};

#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n) for (int i=0;i<(n);i++)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
#define mp make_pair
#define fi first
#define sc second
#define INF 1000000000
ll n;
ll dp[3000][30000];
bool hurui[20001];

void gethurui(bool hurui[],ll n){
	hurui[0] = hurui[1] = false;
	for(ll i = 2;i <= n;i++)
		hurui[i] = true;
	for(ll i = 2;i <= int(sqrt(n) + 0.1);i++){
		if(!hurui[i])
			continue;
		for(ll j = i * 2;j <= n;j += i)
			hurui[j] = false;
	}
}

vector< ll > p;

int main(){
	cin >> n;
	if(n == 1){
		cout << -1 << endl;
		return 0;
	}

	gethurui(hurui,n);
	REP(i,n + 1){
		if(hurui[i])
			p.pb(i);
	}
	ll ps = p.size();

	REP(i,n + 1){
		dp[0][i] = (i == p[0]) ? 1 : -INF;
	}
	dp[0][0] = 0;

	FOR(i,1,ps){
		REP(j,n+1){
			if(j < p[i]){
				dp[i][j] = dp[i - 1][j];
				continue;
			}

			dp[i][j] = max(dp[i - 1][j - p[i]] + 1,dp[i - 1][j]);
		}
	}

	cout << ((dp[ps - 1][n] > 0) ? dp[ps - 1][n] : -1) << endl;
	return 0;

}