#include<bits/stdc++.h>

using namespace std;
typedef unsigned int uint;
typedef long long int ll;
typedef unsigned long long int ull;

#define debugv(v) printf("L%d %s => ",__LINE__,#v);for(auto e:v){cout<<e<<" ";}cout<<endl;
#define debugm(m) printf("L%d %s is..\n",__LINE__,#m);for(auto v:m){for(auto e:v){cout<<e<<" ";}cout<<endl;}
#define debuga(m,w) printf("L%d %s is => ",__LINE__,#m);for(int x=0;x<(w);x++){cout<<(m)[x]<<" ";}cout<<endl;
#define debugaa(m,w,h) printf("L%d %s is..\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){cout<<(m)[x][y]<<" ";}cout<<endl;}
#define ALL(v) (v).begin(),(v).end()
#define BIGINT 0x7FFFFFFF
#define E107 1000000007
void printbit(int u){if(u==0)cout<<0;else{int s=0,k=0;for(;0<u;u>>=1,k++)s=(s<<1)|(u&1);for(;0<k--;s>>=1)cout<<(s&1);}}

#define TIME chrono::system_clock::now()
#define MILLISEC(t) (chrono::duration_cast<chrono::milliseconds>(t).count())

template<typename T1,typename T2>
ostream& operator <<(ostream &o,const pair<T1,T2> p){o<<"("<<p.first<<":"<<p.second<<")";return o;}

vector<int> nonprime;
vector<int> primelist;

void gen_primelist(vector<int>& out, int high){
    int i,j;
    out.resize(high+1);
    out[0] = out[1] = 1;
    int sqh = (int)sqrt(high);
    for (i=2; i<=sqh+1; i++){
        if (out[i] == 0){
            for (j=i*i; j<=high; j+=i){ // i*i
                out[j] = 1;
            }
        }
    }
}

int width,height;
int m,n;

int dp[40010];

int main(){
    int i,j,k;
    int x,y,a,b;
    
    cin >> n;
    
    gen_primelist(nonprime,n);
    primelist.reserve(2000);
    for (i=2;i<=n;i++){
        if (!nonprime[i])
            primelist.push_back(i);
    }
    m = primelist.size();
    
    dp[0]=1;
    
    int high=0;
    for (int slime:primelist){
        for (i=min(high,n-slime);0<=i;i--){
            if (dp[i]==0) continue;
            
            dp[i+slime] = max(dp[i]+1,dp[i+slime]);
            high = max(high,i+slime);
        }
    }
    
    cout << (dp[n]-1) << endl;
    
    return 0;
}