#include <bits/stdc++.h>
using namespace std;
typedef pair<int,int> PII;
typedef long long LL;
typedef unsigned long long ULL;
template<class T> inline bool amax (T &a, const T &b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool amin (T &a, const T &b) { if (a > b) { a = b; return 1; } return 0; }
template<class T> ostream& operator << (ostream &os, const vector<T> &v) { os << "["; for (typename vector<T>::const_iterator it = v.begin(); it != v.end(); it++) { os << (it != v.begin() ? ", " : "") << *it; } os << "]"; return os; }
template<class T> ostream& operator << (ostream &os, const set<T> &s) { os << "["; for (typename set<T>::const_iterator it = s.begin(); it != s.end(); it++) { os << (it != s.begin() ? ", " : "") << *it; } os << "]"; return os; }
template<class Key, class Val> ostream& operator << (ostream &os, const map<Key, Val> &m) { os << "{"; for (typename map<Key, Val>::const_iterator it = m.begin(); it != m.end(); it++) { os << (it != m.begin() ? ", " : "") << it->first << ":" << it->second; } os << "}"; return os; }
template<class T, class S> ostream& operator << (ostream &os, const pair<T, S> &p) { os << "(" << p.first << ", " << p.second << ")"; return os; }
template <class Target, class Source> inline Target lexical_cast (const Source &s) { Target t; stringstream ss; ss << s; ss >> t; return t; }

//> v < ^ (clock wise)
int dx[] = {1,0,-1,0};
int dy[] = {0,1,0,-1};
const int INFI = 1<<28;
const long long int INFL = 1LL<<60;
const double INFD = 1e+300;
const float INFF = 1e+100;
const double EPS = 1e-8;

LL f (LL t, LL B, vector<LL> C) {
    LL r = 0;
    for (int i = 0; i < C.size(); i++) {
        if (C[i] > t) B += C[i]-t, r += C[i]-t,C[i] = t;
    }
    for (int i = 0; i < C.size(); i++) {
        B -= t-C[i], r += t-C[i];
    }
    if (B < 0) return INFI;
    return r;
}

int main(){
    cout.setf(ios::fixed); cout.precision(10);
    ios_base::sync_with_stdio(false);
    LL B, N;
    cin >> B >> N;
    vector<LL> C(N);
    for (int i = 0; i < N; i++) cin >> C[i];
    sort(C.begin(), C.end());
    LL cost = 0;
    while (1) {
        LL diff = 0;
        for (int i = 0; i < N-1; i++) {
            if (C[i] != C[i+1]) {
                diff = C[i+1] - C[i];
                break;
            }
        }
        if (diff == 0) {
            cout << cost << endl;
            return 0;
        }
        LL add = min(B, diff);
        C[0] += add;
        B -= add;
        cost += add;
        sort(C.begin(), C.end());
        if (B == 0) break;
    }

    LL sum = 0;
    for (int i = 0; i < N; i++) sum += C[i];
    LL t = sum / N;
    cout << cost + f(t, B, C) << endl;



    return 0;
}