#pragma warning disable

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.Serialization.Formatters.Binary;
using System.Text;
using System.Text.RegularExpressions;
using System.Diagnostics;
using System.Numerics;
using System.Collections;
using System.Timers;

static class MainClass
{
    public static void Main(string[] args)
    {
        var N = Console.ReadLine().ToInt32();

        var ls = GeneratePrimes().Take(2300).ToList();
        var count = ls.Count();
        var dp = new int[count + 10,20010];
        for (int i = 0; i < count; i++)
        {
            for (int j = 0; j < 20010; j++)
            {
                dp[i, j] = -INF;
            }
        }
        dp[0, 0] = 0;
        for (int i = 0; i < count; i++)
        {
            for (int j = 0; j < 20010; j++)
            {
                var item = ls[i];

                if (j - item < 0)
                {
                    dp[i + 1, j] = dp[i, j];
                }
                else
                {
                    dp[i + 1, j] = Math.Max(dp[i, j], dp[i, j - ls[i]] + 1);

                }
            }
        }
        var num = dp[count, N];
        Console.WriteLine(num < 0 ? -1 : num);
        
    }

    public class BoundedBoolArray
    {
        private BitArray _array;
        private int _lower;

        public BoundedBoolArray(int lower, int upper)
        {
            _array = new BitArray(upper - lower + 1);
            _lower = lower;
        }

        public bool this[int index]
        {
            get
            {
                return _array[index - _lower];
            }
            set
            {
                _array[index - _lower] = value;
            }
        }
    }
    public static IEnumerable<int> GeneratePrimes()
    {
        var primes = new List<int>() { 2, 3 };
        foreach (var p in primes)
            yield return p;
        int ix = 0;
        while (true)
        {
            int prime1st = primes[ix];
            int prime2nd = primes[++ix];
            var lower = prime1st * prime1st;
            var upper = prime2nd * prime2nd - 1;
            var sieve = new BoundedBoolArray(lower, upper);
            foreach (var prime in primes.Take(ix))
            {
                var start = (int)Math.Ceiling((double)lower / prime) * prime;
                for (int index = start; index <= upper; index += prime)
                    sieve[index] = true;
            }
            for (int i = lower; i <= upper; i++)
            {
                if (sieve[i] == false)
                {
                    primes.Add(i);
                    yield return i;
                }
            }
        }
    }


    #region ライブラリ
    public static long ToInt64(this string str) => long.Parse(str);
    public static int ToInt32(this string str) => int.Parse(str);
    public static BigInteger ToBigInteger(this string str) => BigInteger.Parse(str);
    public static List<string> SplittedStringToList(this string str) => str.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).ToList();
    public static List<int> SplittedStringToInt32List(this string str) => str.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).Select(x => int.Parse(x)).ToList();
    public static List<BigInteger> SplittedStringToBigInteger(this string str) => str.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).Select(x => BigInteger.Parse(x)).ToList();

    public const int INF = int.MaxValue / 2;
    #endregion
}