#include <bits/stdc++.h>
using namespace std;
#define modulo 1000000007
#define mod(x) (((long long)x)%modulo)



int main(){
	int N;
	cin>>N;
	vector<int> prime(0);
	for(int i=2;i<=N;i++){
		bool f = true;
		for(int j=0;j<prime.size();j++){
			if(i%prime[j]==0){
				f=false;
				break;
			}
		}
		if(f)prime.push_back(i);
	}
	
	vector<vector<int>> dp(prime.size()+1,vector<int>(N+1,0));
	
	for(int i=1;i<=prime.size();i++){
		dp[i][prime[i-1]]=max(dp[i][prime[i-1]],1);
		for(int j=1;j<=N;j++){
			dp[i][j]=max(dp[i][j],dp[i-1][j]);
			if(j-prime[i-1]>=0){
				if(dp[i-1][j-prime[i-1]]>=1){
					dp[i][j]=max(dp[i][j],dp[i-1][j-prime[i-1]]+1);
				}
			}
		}
	}
	
	if(dp[prime.size()][N]==0)cout<<-1<<endl;
	else cout<<dp[prime.size()][N]<<endl;
	
	return 0;
}