// Standard I/O
#include <iostream>
#include <sstream>
#include <cstdio>
// Standard Library
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <cmath>
// Template Class
#include <complex>
#include <string>
#include <vector>
#include <list>
#include <set>
#include <map>
#include <queue>
#include <stack>
// Container Control
#include <algorithm>

using namespace std;

#define rep( i, n ) for( int i = 0; i < n; ++i )
#define irep( i, n ) for( int i = n-1; i >= 0; --i )
#define reep( i, s, n ) for ( int i = s; i < n; ++i )
#define ireep( i, n, s ) for ( int i = n-1; i >= s; --i )
#define foreach(itr, x) for( typeof(x.begin()) itr = x.begin(); itr != x.end(); ++itr)

#define mp( a, b ) make_pair( a, b )
#define pb( a ) push_back( a )
#define all( v ) v.begin(), v.end()
#define fs first
#define sc second
#define vc vector

// for visualizer.html
double SCALE = 1.0;
double OFFSET_X = 0.0;
double OFFSET_Y = 0.0;
#define LINE(x,y,a,b) cerr << "line(" << SCALE*(x) + OFFSET_X << ","	\
	<< SCALE*(y) + OFFSET_Y << ","										\
	<< SCALE*(a) + OFFSET_X << ","										\
	<< SCALE*(b) + OFFSET_Y << ")" << endl;
#define CIRCLE(x,y,r) cerr << "circle(" << SCALE*(x) + OFFSET_X << ","	\
	<< SCALE*(y) + OFFSET_Y << ","										\
	<< SCALE*(r) << ")" << endl;

typedef long long ll;
typedef complex<double> Point;

typedef pair<int, int> pii;
typedef pair<int, pii> ipii;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector< vector<int> > vii;
typedef vector< vector<double> > vdd;

typedef vector<int>::iterator vi_itr;

const int IINF = 1 << 28;
const double INF = 1e30;
const double EPS = 1e-10;
const double PI = acos(-1.0);

// Direction : L U R D
const int dx[] = { -1, 0, 1, 0};
const int dy[] = { 0, -1, 0, 1 };

ll N, B, A[10];
ll solve( ll ave, ll C )
{
	ll ans = 0;
	rep(i, N){
		if( A[i] > ave ){
			C += A[i] - ave;
			ans += A[i] - ave;
		}
		else{
			C -= ave - A[i];
			ans += ave - A[i];
		}
	}
	return (C < 0 ? (1ll << 50) : ans);
}

int main()
{
	cin >> B >> N;
	rep(i, N) cin >> A[i];

	sort( A, A+N, greater<ll>() );

	ll sum = 0;
	rep(i, N) sum += A[i];

	// rep(i, sum+B+1){
	// 	cout << i << " " << solve(i) << endl;
	// }cout << endl;
	
	ll l = 0, r = sum+B+1;
	while( r - l > 1 ){
		ll mid = (l+r)/2;
		ll f1 = solve(mid, B), f2 = solve(mid+1, B);

		if( f1 - f2 > 0 ) l = mid;
		else r = mid;
	}
	
	cout << min(solve(l, B), solve(l+1, B)) << endl;
}