#include <bits/stdc++.h>
using namespace std;
using i64 = long long;
#define rep(i,s,e) for(int (i) = (s);(i) <= (e);(i)++)

int N;

int prime[20202];
void init(){
  rep(i,2,N){
    if(prime[i] == 0){
      prime[i] = 1;
      for(int j = i + i;j <= N;j+=i) prime[j] = -1;
    }
  }
}

int main(){
  cin >> N;
  init();
  vector<int> dp(N + 1,-1);
  dp[0] = 0;
  rep(i,2,N){
    if(prime[i] == 1){
      vector<int> next = dp;
      rep(j,i,N){
        if(dp[j - i] == -1) continue;
        next[j] = max(next[j],dp[j - i] + 1);
      }
      swap(dp,next);
    }
  }
  cout << dp[N] << endl;
}