#include<bits/stdc++.h>
using namespace std;
#define ALL(x) x.begin(),x.end()
#define rep(i,n) for(int i=0;i<n;i++)
#define INF 1000000000
#define mod 1000000007
typedef long long ll;
const ll LINF = 1001002003004005006ll;
int dx[]={1,0,-1,0};
int dy[]={0,1,0,-1};
int gcd(int a,int b){return b?gcd(b,a%b):a;}

ll maxNum=20001;
vector<bool> isPrime(maxNum,true);
void sieve(ll n){
    isPrime[0]=false;
    isPrime[1]=false;

    for(ll i=2;i<n;i++){
        if(!isPrime[i]) continue;
        for(int j=i*2;j<=n;j+=i)    isPrime[j]=false;
    }
}
int main(){
    int n;
    cin>>n;
    sieve(20001);
    vector<ll> prime_list;
    rep(i,20001){
        if(isPrime[i]) prime_list.push_back(i); 
    }
    vector<ll> dp(100000,-1);
    dp[0]=0;
    for(auto p : prime_list){
        for(int i=20000;i>=0;i--){
            if(dp[i]<0) continue;
            if(dp[i+p]<dp[i]+1)
            dp[i+p]=dp[i]+1;
        }
    }
    cout<<dp[n]<<endl;
    return 0;
}