#include <bits/stdc++.h>
using namespace std;

#define all(c) ((c).begin()), ((c).end())
#define dump(c) cerr << "> " << #c << " = " << (c) << endl;
#define iter(c) __typeof((c).begin())
#define tr(i, c) for (iter(c) i = (c).begin(); i != (c).end(); i++)
#define REP(i, a, b) for (int i = a; i < (int)(b); i++)
#define rep(i, n) REP(i, 0, n)
#define mp make_pair
#define fst first
#define snd second
#define pb push_back
#define debug( fmt, ... ) \
        fprintf( stderr, \
                  fmt "\n", \
                  ##__VA_ARGS__ \
        )

typedef unsigned int uint;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef vector<vi> vvi;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<string> vs;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const int INF = 1 << 29;
const double EPS = 1e-10;

double zero(double d) {
    return d < EPS ? 0.0 : d;
}
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return true; } return false; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return true; } return false; }
#define UNIQUE(v) v.erase( unique(v.begin(), v.end()), v.end() );

template<typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
    return os << '(' << p.first << ',' << p.second << ')';
}

template<typename T>
ostream &operator<<(ostream &os, const vector<T> &a) {
    os << '[';
    rep(i, a.size()) os << (i ? " " : "") << a[i];
    return os << ']';
}

string toString(int i) {
    stringstream ss;
    ss << i;
    return ss.str();
}

const int MOD = 1000000007;
// a^k
ll fpow(ll a, ll k, int M) {
    ll res = 1ll;
    ll x = a;
    while (k != 0) {
        if ((k & 1) == 1)
            res = (res * x) % M;
        x = (x * x) % M;
        k >>= 1;
    }
    return res;
}

struct prepare {
    prepare() {
        cout.setf(ios::fixed, ios::floatfield);
        cout.precision(8);
        ios_base::sync_with_stdio(false);
    }
} _prepare;

ll solve(ll med, vi& C) {
    ll now = 0;
    tr(it, C)
        now += abs(med - *it);
    return now;
}

int main() {
    int B, N;
    cin >> B >> N;
    vi C(N);
    rep(i, N)
        cin >> C[i];
    ll sum = accumulate(all(C), 0ll);
    ll mx = B + sum;

    ll lb = -1;
    ll ub = mx+2;

    while(ub - lb > 2) {
        ll l_med = (lb + lb + ub) / 3;
        ll r_med = (lb + ub + ub) / 3;

        if(r_med * N > mx) {
            ub = r_med;
            continue;
        }
        if(l_med * N > mx) {
            lb = l_med;
            continue;
        }

        ll left = solve(l_med, C);
        ll right = solve(r_med, C);

        if(left <= right)
            ub = r_med;
        else
            lb = l_med;
    }

    cout << solve((lb+ub)/2, C) << endl;

    return 0;
}