import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.io.PrintWriter; import java.util.*; import java.util.stream.IntStream; import java.util.stream.LongStream; public class Main { void solve() throws IOException { long b = nl(); int n = ni(); long[] c = nla(n); Arrays.sort(c); long t = Math.min((LongStream.of(c).sum() + b) / n, c[n / 2]); out.println(LongStream.of(c).map(x -> Math.abs(t - x)).sum()); } String ns() throws IOException { while (!tok.hasMoreTokens()) { tok = new StringTokenizer(in.readLine(), " "); } return tok.nextToken(); } int ni() throws IOException { return Integer.parseInt(ns()); } long nl() throws IOException { return Long.parseLong(ns()); } double nd() throws IOException { return Double.parseDouble(ns()); } String[] nsa(int n) throws IOException { String[] res = new String[n]; for (int i = 0; i < n; i++) { res[i] = ns(); } return res; } int[] nia(int n) throws IOException { int[] res = new int[n]; for (int i = 0; i < n; i++) { res[i] = ni(); } return res; } long[] nla(int n) throws IOException { long[] res = new long[n]; for (int i = 0; i < n; i++) { res[i] = nl(); } return res; } static BufferedReader in; static PrintWriter out; static StringTokenizer tok; public static void main(String[] args) throws IOException { in = new BufferedReader(new InputStreamReader(System.in)); out = new PrintWriter(System.out); tok = new StringTokenizer(""); Main main = new Main(); main.solve(); out.close(); } }