#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)

long long calc(const vector<long long> &v, long long t) {
  long long ret = 0;
  for (long long x: v)
    ret += abs(x - t);
  return ret;
}

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int n;
  long long b;

  cin >> b >> n;
  vector<long long>c(n);
  REP (i, n) cin >> c[i];

  sort(c.begin(), c.end());
  long long sum = 0;
  REP (i, n) sum += c[i];
  
  long long ret = calc(c, (sum + b) / n);
  if (sum >= n * c[n/2])
    ret = min(ret, calc(c, c[n/2]));
  cout << ret << endl;
  
  return 0;
}