#include <bits/stdc++.h>
#define syosu(x) fixed<<setprecision(x)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> P;
typedef pair<double,double> pdd;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<string> vs;
typedef vector<P> vp;
typedef vector<vp> vvp;
typedef vector<pll> vpll;
typedef pair<int,P> pip;
typedef vector<pip> vip;
const int inf=1<<30;
const ll INF=1ll<<60;
const double pi=acos(-1);
const double eps=1e-9;
const ll mod=1e6+7;
const int dx[4]={0,1,0,-1},dy[4]={1,0,-1,0};

ll m,n;
vl a;

int main(){
	cin>>m>>n;
	a=vl(n);
	for(int i=0;i<n;i++) cin>>a[i];
	sort(a.begin(),a.end());
	ll l=0,r=inf;
	while(r-l>1){
		ll M=(l+r)/2,t=m;
		for(auto i:a) t+=i-M;
		if(t>=0) l=M;
		else r=M;
	}
	if(a[n/2]<l) l=a[n/2]; 
	ll res=0;
	for(auto i:a) res+=abs(i-l);
	cout<<res<<endl;
}