#include <algorithm>
#include <cmath>
#include <climits>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <cassert>

using namespace std;

#define LOG(...) printf(__VA_ARGS__)
//#define LOG(...)
#define FOR(i,a,b) for(int i=(int)(a);i<(int)(b);++i)
#define REP(i,n) for(int i=0;i<(int)(n);++i)
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(),(a).rend()
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())
#define RSORT(c) sort((c).rbegin(),(c).rend())
#define CLR(a) memset((a), 0 ,sizeof(a))

typedef long long ll;
typedef unsigned long long ull;
typedef vector<bool> vb;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vb> vvb;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const int dx[] = {-1,0,1,0}; const int dy[] = {0,1,0,-1};

int main() {
    ll have, box_n;

    cin >> have >> box_n;
    vll boxes(box_n);

    REP(i, box_n){
        cin >> boxes[i];
    }
    SORT(boxes);
    ll trg = boxes[min(boxes.size()/2, boxes.size())];

    ll able = -1, cnt = 0;
    while(able < 0) {
        able = have;
        cnt = 0;
        for (auto n:boxes) {
            ll d = n - trg;
            able += d;
            cnt += abs(d);
        }
//        LOG("%d %d %d\n", able, cnt, trg);
        trg+=able/box_n-1;
    }
    cout << cnt << endl;
}