#include <iostream>
#include <algorithm>
using namespace std;
using i64 = long long;

class range {private: struct I{int x;int operator*(){return x;}bool operator!=(I& lhs){return x<lhs.x;}void operator++(){++x;}};I i,n;
public:range(int n):i({0}),n({n}){}range(int i,int n):i({i}),n({n}){}I& begin(){return i;}I& end(){return n;}};

vector<i64> c;
int n;
const i64 inf = 987654321987654321;

i64 calc(i64 p) {
  i64 res = 0;
  for(int i : range(n)) { res += abs(p - c[i]); }
  return res;
}

int main(void) {
  i64 b; scanf("%lld%d", &b, &n);
  c.assign(n, 0);
  i64 summa = b;
  for(int i : range(n)) {
    scanf("%lld", &c[i]);
    summa += c[i];
  }
  sort(c.begin(), c.end());
  i64 lo = 0, hi = summa / n;
  while(hi - lo > 10) {
    i64 m1 = (lo + lo + hi) / 3,
        m2 = (lo + hi + hi) / 3;
    i64 r1 = calc(m1),
        r2 = calc(m2);
    if(r1 > r2) {
      lo = m1;
    } else {
      hi = m2;
    }
  }
  i64 res = inf;
  for(i64 x : range(lo, hi+1)) {
    res = min(res, calc(x));
  }
  printf("%lld\n", res);
  return 0;
}