#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <numeric>
#include <functional>
#include <cmath>
#include <queue>
#include <stack>
#include <set>
#include <map>

#define repd(i,a,b) for (int i=(a);i<(b);i++)
#define rep(i,n) repd(i,0,n)
typedef long long ll;

using namespace std;


int inputValue(){
    int a;
    cin >> a;
    return a;
};

template <typename T>
void output(T a, int precision) {
    if(precision > 0){
        cout << setprecision(precision)  << a << "\n";
    }
    else{
        cout << a << "\n";
    }
}

int main() {
    
    // source code
    int B = inputValue(); // 手持ち
    ll N; // 箱の数
    ll num = B; // 合計の数
    cin >> N;
    vector<int> C(N);
    rep(i, N){
        C[i] = inputValue(); // 各箱の中の数
        num += C[i];
    }
    
    ll low = 0;
    ll high = num / N;
    
    ll lcnt = 0;
    ll hcnt = 0;
    
    while (low + 2 < high) {
        ll lmid = (2 * low + high) / 3;
        ll hmid = (low + 2 * high) / 3;
        
        lcnt = 0;
        hcnt = 0;
        
        rep(i, N){
            lcnt += abs(C[i] - lmid);
            hcnt += abs(C[i] - hmid);
        }
        
        if (lcnt > hcnt) {
            low = lmid;
        }
        else{
            high = hmid;
        }
    }
    ll lmid = low + 1;
    ll hmid = low + 2;
    
    lcnt = 0;
    ll lmcnt = 0;
    ll hmcnt = 0;
    hcnt = 0;
    rep(i, N){
        lcnt += abs(C[i] - low);
        lmcnt += abs(C[i] - lmid);
        hmcnt += abs(C[i] - hmid);
        hcnt += abs(C[i] - high);
    }
    
    output(min(min(lcnt, lmcnt), min(hmcnt, hcnt)), 0);
    
    return 0;
}