#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i = (a); i < (b); ++i)
#define REP(i,n) FOR(i,0,n)
#define RREP(i,n) for(int i = (n) - 1; (i) >= 0; --i)
#define SZ(n) (int)(n).size()
#define ALL(n) (n).begin(), (n).end()
#define MOD LL(1e9 + 7)
#define INF 1000000
using namespace std;
typedef long long LL;
typedef vector<int> VI;
typedef pair<int, int> PI;

int b, n;
int c[16];

LL f(LL x) {
	LL tmp = 0;
	LL a = b;
	REP(i, n) {
		tmp += abs(x - c[i]);
		a += c[i] - x;
	}
	if (a < 0) return LLONG_MAX;
	return tmp;
}

int main() {
	cin >> b >> n;
	LL t = b;
	REP(i, n) {
		cin >> c[i];
		t += c[i];
	}
	LL l = 0, r = t / n;
	while(r - l > 10) {
		LL nr = (r * 2 + l) / 3;
		LL nl = (r + l * 2) / 3;
		if (f(nr) >= f(nl)) {
			r = nr;
		}
		else {
			l = nl;
		}
	}
	LL ans = LLONG_MAX;
	REP(i, 100) {
		ans = min(ans, f(l - 50 + i));
	}
	cout << ans << endl;
	return 0;
}