using System;
using System.IO;
using System.Linq;
using System.Text;
using System.Collections.Generic;
using System.Diagnostics;
using System.Numerics;
using Enu = System.Linq.Enumerable;

class Program
{
    public void Solve()
    {
        var N = BigInteger.Parse(Reader.String());
        if (N <= 100) Console.WriteLine(BruteForce((int)N));
        else if (N % 8 == 1 && MillerRabin.IsPrime(N - 8)) Console.WriteLine(14);
        else Console.WriteLine(8);
    }

    int BruteForce(int N)
    {
        for (int W = 3; W < N; W++)
            if (Can(N, W))
                return W;
        return N;
    }

    private bool Can(int N, int W)
    {
        var seen = Sieve(N);
        var que = new Queue<int>();
        que.Enqueue(1);
        Action<int> Add = x => { seen[x] = true; que.Enqueue(x); };

        while (que.Count > 0)
        {
            int val = que.Dequeue();
            if (val == N) return true;
            seen[val] = true;
            int c = (val - 1) % W;
            if (val > 1 && c - 1 >= 0 && !seen[val - 1]) Add(val - 1);
            if (c + 1 < W && !seen[val + 1]) Add(val + 1);
            if (val + W <= N && !seen[val + W]) Add(val + W);
            if (val >= W && !seen[val - W]) Add(val - W);
        }

        return false;
    }

    static bool[] Sieve(int n)
    {
        bool[] primes = new bool[n + 1];
        bool[] composite = new bool[n + 1];
        for (int i = 2; i <= n; i++)
        {
            if (composite[i]) continue;
            primes[i] = true;
            for (int j = i + i; j <= n; j += i) composite[j] = true;
        }
        return primes;
    }


    class MillerRabin
    {
        private static readonly Random random = new Random(0);
        private static readonly int MaxTest = 15;

        public static bool IsPrime(BigInteger n)
        {
            if (n == 2) return true;
            if (n <= 1 || n % 2 == 0) return false;
            var d = n - 1;
            int s = 0;
            while (d % 2 == 0) { d /= 2; s++; }
            for (int t = 0; t < MaxTest; t++)
            {
                var a = (ulong)(((long)random.Next() << 32) + random.Next()) % (n - 1) + 1;
                var x = BigInteger.ModPow(a, d, n);
                if (x == 1) continue;
                bool found = false;
                for (int r = 0; r < s; r++)
                {
                    if (x == n - 1) { found = true; break; }
                    x = x * x % n;
                }
                if (!found) return false;
            }
            return true;
        }
    }

}


class Entry { static void Main() { new Program().Solve(); } }
class Reader
{
    private static TextReader reader = Console.In;
    private static readonly char[] separator = { ' ' };
    private static readonly StringSplitOptions op = StringSplitOptions.RemoveEmptyEntries;
    private static string[] A = new string[0];
    private static int i;
    private static void Init() { A = new string[0]; }
    public static void Set(TextReader r) { reader = r; Init(); }
    public static void Set(string file) { reader = new StreamReader(file); Init(); }
    public static bool HasNext() { return CheckNext(); }
    public static string String() { return Next(); }
    public static int Int() { return int.Parse(Next()); }
    public static long Long() { return long.Parse(Next()); }
    public static double Double() { return double.Parse(Next()); }
    public static int[] IntLine() { return Array.ConvertAll(Split(Line()), int.Parse); }
    public static int[] IntArray(int N) { return Enu.Range(0, N).Select(i => Int()).ToArray(); }
    public static int[][] IntTable(int H) { return Enu.Range(0, H).Select(i => IntLine()).ToArray(); }
    public static string[] StringArray(int N) { return Enu.Range(0, N).Select(i => Next()).ToArray(); }
    public static string Line() { return reader.ReadLine().Trim(); }
    private static string[] Split(string s) { return s.Split(separator, op); }
    private static string Next() { CheckNext(); return A[i++]; }
    private static bool CheckNext()
    {
        if (i < A.Length) return true;
        string line = reader.ReadLine();
        if (line == null) return false;
        if (line == "") return CheckNext();
        A = Split(line);
        i = 0;
        return true;
    }
}