#include <bits/stdc++.h>
using namespace std;

// 基本テンプレート
struct cww{cww(){ios::sync_with_stdio(false);cin.tie(0);}}star;
#define P(x) cout << (x) << endl
#define p(x) cout << (x)
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define mat(type, c, m, n) vector<vector<type>> c(m, vector<type>(n));for(auto& r:c)for(auto& i:r)cin>>i;
#define rep(i,a,n) for(int i=(a), i##_len=(n); i<i##_len; ++i)
#define rrep(i,a,n) for(int i=(a); i>n; --i)
#define each(x,y) for(auto &(x):(y))
#define perm(c) sort(all(c));for(bool c##p=1;c##p;c##p=next_permutation(all(c)))
#define cauto const auto&
#define UNIQUE(v) v.erase( unique(all(v)), v.end() );
#define len(x) ((int)(x).size())
#define length(a)   (sizeof(a)/sizeof(a[0]))
#define mp make_pair
#define eb emplace_back
template<typename T> inline bool inside(T y, T x, T h, T w) { return 0 <= y && y < h && 0 <= x && x < w; };
template<typename T, typename U> bool chmin(T& a, U b) {return a > b ? a = b, true : false;}
template<typename T, typename U> bool chmax(T& a, U b) {return a < b ? a = b, true : false;}

// デバッグ用
template <class T> inline void print(T t){cout << t << endl;}
template <class H, class... T> inline void print(H h, T... t){cout << h << " ";print(t...);}
#define dbg(v) for(auto i : v) { cout << i << " "; } cout << endl;

// 型
typedef long long ll;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector<long long> vll;
typedef vector<string> vs;
typedef vector<bool> vb;

// 定数
#define PI acos(-1.0)
//constexpr int EPS = (1e-9);
//constexpr int INF = 100000000;

// 4近傍
//constexpr int dx[] = {1, 0, -1, 0};
//constexpr int dy[] = {0, 1, 0, -1};

// 8近傍
//constexpr int dy[]={0,0,1,-1,1,1,-1,-1};
//constexpr int dx[]={1,-1,0,0,1,-1,1,-1};

//constexpr int mod = 1000000000;

//constexpr int MAX = 1000001;

inline ll f() {
	ll b, n; cin >> b >> n;
	if(n == 1) return 0;

	vll c(n); rep(i, 0, n) cin >> c[i];
	ll sum = accumulate(all(c), 0);
	ll avg = sum / n;
	if((sum - avg * n) > (sum + b - avg * n)) avg = (sum + b) / n;

	ll ans = 0;
	rep(i, 0, n) {
		ans += abs(avg - c[i]);
	}

	return ans;
}

int main() {
//	cout << setprecision(15) << fixed;

	P(f());

	return 0;
}