#include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <cmath>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <bitset>
using namespace std;
#define FOR(I,A,B) for(int I = (A); I < (B); ++I)
typedef long long ll;

// 揃える数を決めて三分探索
ll B, N;
ll C[100];
// xで揃えた時の回数
ll calc (ll x) {
  ll ret = 0;
  FOR(i,0,N){
    ret += max(C[i] - x, x - C[i]);
  }
  return ret;
}

int main(){
  cin >> B >> N;
  ll csum = 0;
  FOR(i,0,N){
    cin >> C[i];
    csum += C[i];
  }
  if(N == 1){
    cout << 0 << endl;
    return 0;
  }

  ll l = 0, r = (B + csum) / N;
  while(r - l > 3){
    ll ml = (r + 2 * l) / 3;
    ll mr = (2 * r + l) / 3;
    if(calc(ml) <= calc(mr)) r = mr;
    else l = ml;
  }
  ll ans = 1000000000000000LL;
  for(ll i = l; i <= r; i++) ans = min(ans, calc(i));
  cout << ans << endl;
  return 0;
}