#include <bits/stdc++.h>
using namespace std;

#define int long long
#define rep(i,l,r) for(int i=(int)(l);i<(int)(r);i++)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)x.size())
template<class T>bool chmax(T &a,T b){if(a<b){a=b;return 1;}return 0;}
template<class T>bool chmin(T &a,T b){if(a>b){a=b;return 1;}return 0;}

typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;

const int inf = 1LL<<60;
const int mod = 1e9 + 7;
const double eps = 1e-9;

/*{
  }*/

int b, n, c[10];

int f(int x){
  int res = 0;
  rep(i, 0, n) res += abs(c[i]-x);
  return res;
}

signed main(){
  cin >> b >> n;
  int sum = b;
  rep(i, 0, n){
    cin >> c[i];
    sum += c[i];
  }

  if(n == 1){
    cout << 0 << endl;
    return 0;
  }

  sort(c, c+n);
  int l = c[0], r = sum/n+1;
  rep(i, 0, 1000){
    int x1 = (l+l+r)/3;
    int x2 = (l+r+r)/3;
    if(f(x1) < f(x2)) r = x2;
    else l = x1;
  }

  int ans = inf;
  rep(i, l, r) chmin(ans, f(i));
  cout << ans << endl;

  return 0;
}