using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using System.IO;

class Program
{
    static void Main()
    {
        new Magatro().Solve();
    }
}

public class Scanner
{
    private StreamReader Sr;

    private string[] S;
    private int Index;
    private const char Separator = ' ';

    public Scanner(Stream source)
    {
        Index = 0;
        S = new string[0];
        Sr = new StreamReader(source);
    }

    private string[] Line()
    {
        return Sr.ReadLine().Split(Separator);
    }

    public string Next()
    {
        string result;
        if (Index >= S.Length)
        {
            S = Line();
            Index = 0;
        }
        result = S[Index];
        Index++;
        return result;
    }
    public int NextInt()
    {
        return int.Parse(Next());
    }
    public double NextDouble()
    {
        return double.Parse(Next());
    }
    public long NextLong()
    {
        return long.Parse(Next());
    }
    public decimal NextDecimal()
    {
        return decimal.Parse(Next());
    }
    public string[] StringArray(int index = 0)
    {
        Next();
        Index = S.Length;
        return S.Skip(index).ToArray();
    }
    public int[] IntArray(int index = 0)
    {
        return StringArray(index).Select(int.Parse).ToArray();
    }
    public long[] LongArray(int index = 0)
    {
        return StringArray(index).Select(long.Parse).ToArray();
    }
    public bool EndOfStream
    {
        get { return Sr.EndOfStream; }
    }
}

public class Magatro
{
    private int M;
    private int N;
    private int[] C;

    private int[] Arr;
    private int[] Primes;

    private void Scan()
    {
        var cin = new Scanner(Console.OpenStandardInput());
        M = cin.NextInt();
        N = cin.NextInt();
        C = cin.IntArray();
    }

    private void PrimeCalc()
    {
        bool[] num = new bool[M + 1];
        num[0] = true;
        num[1] = true;
        for (int i = 2; i * i <= M; i++)
        {
            if (!num[i])
            {
                for (int j = i + i; j <= M; j += i)
                {
                    num[j] = true;
                }
            }
        }

        var list = new List<int>();
        for (int i = 0; i <= M; i++)
        {
            if (!num[i])
            {
                list.Add(i);
            }
        }
        Primes = list.ToArray();
    }

    public void Solve()
    {
        Scan();
        Arr = (new int[M + 1]).Select(i => -1).ToArray();
        Arr[M] = 0;
        for (int i = M; i >= 0; i--)
        {
            if (Arr[i] == -1) continue;
            foreach (int j in C)
            {
                if (i - j < 0) continue;
                Arr[i - j] = Math.Max(Arr[i - j], Arr[i] + 1);
            }
        }

        PrimeCalc();

        int ans = 0;

        foreach(int i in Primes)
        {
            if (Arr[i] == -1) continue;
            ans += Arr[i];
        }

        ans += Arr.Max();
        Console.WriteLine(ans);
    }
}