#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <complex>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <iomanip>
#include <assert.h>
#include <array>
#include <cstdio>
#include <cstring>
#include <random>
#include <functional>
#include <numeric>
#include <bitset>

using namespace std;

#define REP(i,a,b) for(int i=a;i<(int)b;i++)
#define rep(i,n) REP(i,0,n)
#define all(c) (c).begin(), (c).end()
#define zero(a) memset(a, 0, sizeof a)
#define minus(a) memset(a, -1, sizeof a)
#define minimize(a, x) a = std::min(a, x)
#define maximize(a, x) a = std::max(a, x)

typedef long long ll;
int const inf = 1<<29;

typedef __int128_t INT;

INT N;

set<INT> carmichael = {
  561, 1105, 1729, 2465, 2821, 6601, 8911, 10585, 15841, 29341, 41041, 46657, 52633, 62745, 63973, 75361, 101101, 115921, 126217, 162401, 172081, 188461, 252601, 278545, 294409, 314821, 334153, 340561, 399001, 410041, 449065, 488881, 512461, 530881, 552721, 656601, 658801, 670033, 748657, 825265, 838201, 852841, 997633, 1024651, 1033669, 1050985, 1082809, 1152271, 1193221, 1461241, 1569457, 1615681, 1773289, 1857241, 1909001, 2100901, 2113921, 2433601, 2455921, 2508013, 2531845, 2628073, 2704801, 3057601, 3146221, 3224065, 3581761, 3664585, 3828001, 4335241, 4463641, 4767841, 4903921, 4909177, 5031181, 5049001, 5148001, 5310721, 5444489, 5481451, 5632705, 5968873, 6049681, 6054985, 6189121, 6313681, 6733693, 6840001, 6868261, 7207201, 7519441, 7995169, 8134561, 8341201, 8355841, 8719309, 8719921, 8830801, 8927101, 9439201, 9494101, 9582145, 9585541, 9613297, 9890881
};

INT pow(INT x, INT n, INT M){
  INT tmp = 1;

  if ( n > 0 ){
    tmp = pow(x, n/2, M);
    if ( n%2 == 0 ) tmp = (tmp*tmp)%M;
    else tmp = (((tmp*tmp)%M)*x)%M;
  }
  return tmp;
}

bool is_prime(INT const& x) {
  if(carmichael.count(x)) { return false; }
  if(x == 2) { return 1; }
  if(x < 2 || (x%2 == 0)) { return 0; }
  return pow(2, x-1, x) == 1;
}

map<INT, int> mp = {
{4,3}, 
{6,5}, 
{8,7}, 
{9,7}, 
{10,7}, 
{12,11}, 
{14,13}, 
{15,7}, 
{16,7}, 
{18,8}, 
{20,19}, 
{21,19}, 
{22,7}, 
{24,23}, 
};

vector<int> wlist = {
  8, 14, 17, 19, 20, 23, 24, 25, 26, 27, 31 ,32 ,33, 34, 37 , 38
};

int main() {

  string s; cin >> s;
  INT N = 0;
  rep(i, s.size()) {
    N *= 10;
    N += s[i] - '0';
  }

  if(mp.find(N) != mp.end()) {
    cout << mp[N] << endl;
    exit(0);
  }

  if((N % 8 == 1 || is_prime(N-1)) && is_prime(N-8)) {
    int idx = 1;
    while(!(N % 8 == 1 || is_prime(N-1)) && is_prime(N-8)) idx++;
    cout << wlist[idx] << endl;
  }
  else {
    cout << 8 << endl;
  }

  return 0;
}