#include <iostream>
#include <vector>
using namespace std;
struct SieveEratos{
  vector<int> t;
  SieveEratos(int n):t(n+1,true){
    t[0] = t[1] = 1;
    for(int i = 2; n >= i; i++){
      if(t[i]){
        for(int j = i+i; n >= j; j+=i){
          t[j] = 0;
        }
      }
    }
  }
  bool operator[](int x){return t[x];}
};
vector<vector<int>> dp(3000,vector<int>(20000,-1));
int main(){
  int n;cin>>n;
  SieveEratos A(n+1);
  vector<int> B;
  for(int i = 2; n >= i; i++){
    if(A[i])B.push_back(i);
  }
  dp[0][0] = 0;
  for(int i = 0; B.size() > i; i++){
    for(int j = 0; n >= j; j++){
      if(dp[i][j] == -1)continue;
      if(j+B[i] <= n)dp[i+1][j+B[i]] = max(dp[i+1][j+B[i]],dp[i][j]+1);
      dp[i+1][j] = max(dp[i+1][j],dp[i][j]);

    }
  }
  cout << dp[B.size()][n] << endl;
  
}