#include <iostream>
#include <utility>
#include <vector>
#include <string>
#include <cmath>
#include <algorithm>
#include <functional>
#include <iomanip>
#include <map>
#include <set>
#include <queue>
#include <complex>
#include <cassert>
using namespace std;
using ll = long long int;
#define CHMAX(x,y)  (x) = ((x) > (y)) ? (x) : ((x) = (y));
#define CHMIN(x,y)  (x) = ((x) < (y)) ? (x) : ((x) = (y));
#define REP(i,n) for(int (i)=0;(i)<(n);++(i))
#define RREP(i,n,N) for(int (i)=(n);(i)<(N);++(i))
#define DREP(i,n) for(int (i)=(n);(i)>=0;--(i))
#define DRREP(i,n,N) for(int i=(n);(i)>=(N);--(i))
const int INF = 1e9;
const ll INFL = 1e18;
const int Mod = 1e9 + 7;
const int dx[] = {0,1,0,-1};
const int dy[] = {1,0,-1,0};


int main(int argc, char const *argv[])
{
  ll B,N; cin >> B >> N;
  vector<ll> C(N);
  REP(i,N)cin >> C[i];
  auto f = [&](ll K)->ll
  {
    ll res = 0;
    REP(i,N)res += abs(C[i]-K);
    return res;
  };
  sort(C.begin(),C.end());
  ll low = C[0],high = B; 
  REP(i,N)high += C[i];
  high = ((high + N-1)/N);

  while(high - low > 3)
  {
    ll c1 = (2*low + high)/3;
    ll c2 = (low + 2*high)/3;
    if(f(c1) < f(c2))high = c2;
    else low = c1;
  }

  ll answer = INFL;
  RREP(i,low,high)CHMIN(answer,f(i));
  std::cout << answer << std::endl;
}