using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Text;
using System.Text.RegularExpressions;
using System.Linq;

class Magatro
{
    static int[] Primes;
    static int N = int.Parse(Console.ReadLine());
    static void Main()
    {
        PrimeCalc();
        int[,] B = new int[20001, Primes.Length + 1];
        for(int i = 0; i <= N; i++)
        {
            for(int j = 0; j <= Primes.Length;j++)
            {
                B[i, j] = -1;
            }
        }
        B[0, 0] = 0;
        for(int i = 0; i < Primes.Length; i++)
        {
            for(int j = 0; j <= N; j++)
            {
                if (B[j, i] == -1)
                {
                    continue;
                }
                
                B[j, i + 1] =Math.Max(B[j, i], B[j, i + 1]);
                if (j + Primes[i] > N)
                {
                    continue;
                }
                if(B[j + Primes[i], i + 1]==-1)
                    B[j + Primes[i], i + 1] = B[j, i] + 1;
                else
                {
                    B[j + Primes[i], i + 1] = Math.Max(B[j, i] + 1, B[j + Primes[i], i + 1]);
                }
            }
        }
       int max = -1;
        for(int i = 1; i <= Primes.Length; i++)
        {
            max = Math.Max(max, B[N,i]);
        }
        Console.WriteLine(max);


    }
    static void PrimeCalc()
    {
        bool[] a = new bool[N + 1];
        a[0] = true;
        a[1] = true;
        for(int i = 2; i <= Math.Sqrt(N); i++)
        {
            if (!a[i])
            {
                for(int j = i * 2; j <= N; j += i)
                {
                    a[j] = true;
                }
            }
        }
        List<int> L = new List<int>();
        for(int i = 0; i <= N; i++)
        {
            if (!a[i])
            {
                L.Add(i);
            }
        }
        Primes = L.ToArray();
    }
}
struct A
{
    public A(int num,int cnt)
    {
        Num = num;
        Cnt = cnt;
    }
    public int Num;
    public int Cnt;
}