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

//repetition
#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define rep(i, n) for(ll i = 0; i < (ll)(n); i++)

//container util
#define all(x) (x).begin(),(x).end()

//typedef
typedef long long ll;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<ll> VLL;
typedef vector<VLL> VVLL;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef pair<ll, ll> PLL;

//const value
//const ll MOD = 1e9 + 7;
//const int dx[] = {0,1,0,-1};//{0,0,1,1,1,-1,-1,-1};
//const int dy[] = {1,0,-1,0};//{1,-1,0,1,-1,0,1,-1};

//conversion
inline int toInt(string s) {int v; istringstream sin(s);sin>>v;return v;}
inline ll toLL(string s) {ll v; istringstream sin(s);sin>>v;return v;}
template<class T> inline string toString(T x) {ostringstream sout;sout<<x;return sout.str();}
VI prime;
void makePrime(){
  bool p[20010];
  memset(p,true,sizeof(p));
  p[0] = false;
  p[1] = false;
  for (size_t i = 2; i < 20010; i++) {
    if(p[i] == false) continue;
    int x = 2;
    while(x*i <= 20000){
      p[i*x] = false;
      x++;
    }
  }

  rep(i,20010) if(p[i]) prime.push_back(i);
}
int main(){
  ios::sync_with_stdio(false);
  cin.tie(0);
  ll n;
  cin  >> n;
  makePrime();
  int dp[20010][2];
  memset(dp,0,sizeof(dp));

  rep(i,prime.size()){
    int p = prime[i];
    int from = i%2;
    int to = (i+1)%2;

    rep(j,20005){
      if(j == 0 || dp[j][from] >= 1){
        if(j + p <= 20000) dp[j+p][to] = max(dp[j+p][from],dp[j][from] + 1);
        dp[j][to] = max(dp[j][to],dp[j][from]);
      }else{
        dp[j][to] = max(dp[j][to],dp[j][from]);
      }
    }
  }

  if(dp[n][0] >= 1 || dp[n][1] >= 1) cout << max(dp[n][0],dp[n][1]) << endl;
  else cout << -1 << endl;
  return 0;
}