#include <bits/stdc++.h>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()

template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<int, pii> P;

const ll INF = 1ll<<60;
const ll MOD = 1000000007;
const double EPS  = 1e-10;

int b, n;
int c[10];

bool ok(ll x) {
	ll cnt = b;
	REP(i, n) cnt += c[i] - x;
	return cnt >= 0;
}

ll cou(ll x) {
	ll res = 0;
	REP(j, n) res += abs(c[j] - x);
	return res;
}

int main() {
	cin >> b >> n;
	REP(i, n) scanf("%d", c + i);
	
	ll ans = INF;
	ll l = -1, r = INF;
	
	REP(i, 300) {
		ll x1 = l + (r - l) / 3;
		ll x2 = r - (r - l) / 3;
		
		bool left = false;
		if (!ok(x2)) left = true;
		
		ll y1 = cou(x1), y2 = cou(x2);
		
		if (ok(x1)) chmin(ans, y1);
		if (ok(x2)) chmin(ans, y2);
		
		if (left) r = x2;
		else if (y1 >= y2) l = x1;
		else r = x2;
	}
	
	cout << ans << endl;
	
	return 0;
}