#include<bits/stdc++.h>
using namespace std;
#define MAXVAL 20000

bool flags[MAXVAL+100];

inline void huga(int i){
  if(flags[i]==false)for(int j = i*i; j <= MAXVAL; j+=i)flags[j]=true;
}
void Sieve_of_Eratosthenes(){
  for(int i = 6; (i-1)*(i-1) <= MAXVAL; i+=6)huga(i-1),huga(i+1);
  for(int i = 6; i <= MAXVAL; i+=6)flags[i]=flags[i+2]=flags[i+3]=flags[i+4]=true;flags[0]=flags[1]=flags[4]=true;
}


int main(){
  int count = 0, N, temp[MAXVAL + 100];
  
  Sieve_of_Eratosthenes();

  /*
  for(int i = 1; i <= MAXVAL; i++){
    if(!flags[i])count++;
  }
  cout<<count<<endl;
*/
  cin>>N;

  temp[0]=0;
  for(int i = 1; i <= MAXVAL; i++)temp[i] = -1;

  for(int j = 1; j <= N; j++){
    if(flags[j])continue;
    for(int i = N; i >= 0; i--){
      if(i+j <= N && temp[i] != -1){
	temp[i+j] = max(temp[i+j],temp[i]+1);
      }
    }
  }

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