#include<bits/stdc++.h>
#define ll long long
#define endl "\n";
using namespace std;
ll sigma(ll w){
    double a;
    a=((double)w/2)*((double)w+1);
    return (ll)a;
}
int main(){
    ll a,b=0,c=0,d,e,f,suma,sumb,will=0;
    cin >>a;
    cin >>b;
    d=2000000000;
    vector <ll> q(b);
    will=a;
    for (int i=0; i<b; i++){
        cin >>q[i];
        will+=q[i];
    }
    d=will/b+1;
    while(d-c>2){
        e=c+(d-c)/3;
        f=c+((d-c)/3)*2;
        suma=0;
        sumb=0;
        for (int j=0; j<b; j++){
            suma+=abs(q[j]-e);
            sumb+=abs(q[j]-f);
        }
        if(suma>sumb){
            c=e;
        }else if(suma<sumb){
            d=f;
        }else {
            c=e;
            d=f;
        }
    }
    // ll min=INT64_MAX,size=4;
    vector <ll> p(4);
    for (int o=0; o<b; o++){
        p[0]+=abs(q[o]-c-1);
        p[1]+=abs(q[o]-c);
        p[2]+=abs(q[o]-d);
        p[3]+=abs(q[o]-d+1);
    }
    cout <<*min_element(p.begin(),p.end())<<endl
    return 0;
}
/*
c e f d
ansa->e
ansb->f
*/