#include <algorithm>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <functional>
#include <iostream>
#include <map>
#include <memory>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>

using namespace std;

#define sz size()
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define all(c) (c).begin(), (c).end()
#define rep(i,a,b) for(int i=(a);i<(b);++i)
#define clr(a, b) memset((a), (b) ,sizeof(a))

#define MOD 1000000007

int isPrime(int n){
  int i;

  if(n < 2){
    return 0;
  }
  else if(n == 2){
    return 1;
  }

  if(n % 2 == 0){
    return 0;
  }
 
  for(i = 3; i * i <= n; i += 2){
    if(n % i == 0){
      return 0;
    }
  }

  return 1;
}

int d[10000][30];

int main(){
  long long n;
  cin>>n;
  int d[100] = {
    -1,-1,-1,-1,3,-1,5,-1,7,7,7,
    -1,11,-1,13,7,7,-1,8,-1,19,
    19,7,-1,23,23,8,8,8,-1,8,
    -1,8,8,8,8,8,-1,8,8,8,
    -1,8,-1,8,8,8,-1,8,14,8,
    8,8,-1,8,8,8,8,8,-1,8,
    -1,8,8,8,8,8,-1,8,8,8,
    -1,8,-1,8,8,8,8,8,-1,8,
    14,8,-1,8,8,8,8,8,-1,8,
    8,8,8,8,8,8,-1,8,8};
  if(n<100){
    cout << d[n] << endl;
    return 0;
  }
  long long a = n-1;
  long long b = n-8;
  if(a%8==0){
    rep(i,2,1000000){
      if(isPrime(i)==1){
        if(b%i==0){
          cout << "8" << endl;
          return 0;
        }
      }
    }
    cout << "14" << endl;
    return 0;
  }
  else{
    cout << "8" << endl;
  }
  return 0;
}