#include <bits/stdc++.h>
using namespace std;
#define int long long
#define INF -1145141919810
#define REP(i,n) for (int i=0;i<(n);i++)
typedef pair<int,int> P;

int N;
int dp[10001][20000]={};
vector<int> prime;
int generate(){
  prime.push_back(2);
  for(int i=3;i<=N;i+=2){
    int k=0;
    for(int j=3;j<=sqrt(i);j+=2){
      if(i%j==0){
        k=1;
        break;
      }
    }
    if(k==0) prime.push_back(i);
  }
  return 0;
}

int solve(int i,int sum){
  if(sum==N) return 0;
  if(i>prime.size()) return INF;
  if(sum>N) return INF;
  if(prime[i]>N) return INF;
  if(dp[i][sum]!=0) return dp[i][sum];
  return dp[i][sum]=max(solve(i+1,sum+prime[i])+1,solve(i+1,sum));
}

signed main(){
  cin>>N;
  generate();
  int ans=solve(0,0);
  if(ans<INF-50000) ans=-1;
  cout<<ans<<endl;
}