#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <array>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <fstream>
#include <complex>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
using namespace std;

using ll = long long;
constexpr int INF = 1001001001;
// constexpr int mod = 1000000007;
constexpr int mod = 998244353;

template<class T>
inline bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class T>
inline bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    ll B;
    int N;
    cin >> B >> N;
    vector<ll> C(N);
    for(int i = 0; i < N; ++i)  cin >> C[i], B += C[i];
    auto f = [&](int x){
        ll res = 0;
        for(int i = 0; i < N; ++i)  res += abs(x - C[i]);
        return res;
    };
    ll lb = 0, ub = B / N;
    for(int loop = 0; loop < 100; ++loop){
        int l = (lb * 2 + ub) / 3;
        int r = (lb + ub * 2) / 3;
        if(f(l) < f(r)) ub = r;
        else    lb = l;
    }
    ll ans = 1e+17;
    for(int m = lb; m <= ub; ++m)   chmin(ans, f(m));
    cout << ans << endl;

    return 0;
}