#include<bits/stdc++.h>
#define rep(i,a) for(int i=(int)0;i<(int)a;++i)
#define rrep(i,a) for(int i=(int)a-1;i>=0;--i)
#define REP(i,a,b) for(int i=(int)a;i<(int)b;++i)
#define RREP(i,a,b) for(int i=(int)a-1;i>=b;--i)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
using ll=long long;
constexpr ll mod = 1e9 + 7;
constexpr ll INF = 1LL << 60;
 
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}


ll gcd(ll n, ll m) {
    ll tmp;
    while (m!=0) {
        tmp = n % m;
        n = m;
        m = tmp;
    }
    return n;
}
 
ll lcm(ll n, ll m) {
    return abs(n) / gcd(n, m)*abs(m);//gl=xy
}

using namespace std;

ll b, n;
vector<ll>c;
ll sum;

ll f(ll x)
{
	ll res = 0;
	if (n * x > sum)
	{
		return INF;
	}
	rep(i,n){
		res += abs(c[i] - x);
	}
	return res;
}

void solve()
{
	cin >> b >> n;
	sum = 0;
	c.resize(n);
	rep(i, n) cin >> c[i], sum += c[i];
	sum += b;
	sort(all(c));
	ll l = c[0], r = c[n - 1];
	while(r-l>(ll)1e3){
		ll x = l + (r - l) / 3, y = r - (r - l) / 3;
		if(f(x)>f(y)){
			l = x;
		}
		else{
			r = y;
		}
	}
	ll ans = 1e18;
	for (ll i = l; i <= r; ++i)
	{
		chmin(ans, f(i));
	}
	cout << ans << endl;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout<<fixed<<setprecision(15);
    solve();
    return 0;
}