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

class Program
{ 
    static void Main(string[]args)
    {
        Magatro m = new Magatro();
        m.Scan();
        m.Solve();
    }
}

public class Scanner
{
    private StreamReader Sr;
    private string[] S;
    private int Index;

    private const char Separator=' ';

    public Scanner()
    {
        Index = 0;
        S = new string[0];
        Sr = new StreamReader(Console.OpenStandardInput());
    }

    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 bool ScanToEnd(ref string s)
    {
        if (Sr.EndOfStream)
        {
            return false;
        }
        else
        {
            s = Sr.ReadLine();
            return true;
        }
    }
}

public class Magatro
{
    private long B, N;
    private long[] C;

    public void Scan()
    {
        Scanner sc = new Scanner();
        B = sc.NextLong();
        N = sc.NextInt();
        C = new long[N];
        for(int i = 0; i < N; i++)
        {
            C[i] = sc.NextLong();
        }
    }

    public void Solve()
    {
        Array.Sort(C);
        long max = (C.Sum() + B) / N;
        long o;
        if (C.Length % 2 == 0)
        {
            o = (C[C.Length / 2] + C[C.Length / 2 - 1]) / 2;
        }
        else
        {
            o = (C[C.Length / 2]);
        }
        long ans = 0;
        for(int i = 0; i < N; i++)
        {
            ans += Math.Abs(Math.Min(max, o) - C[i]);
        }
        Console.WriteLine(ans);
    }

}