import std.conv, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.container, std.math, std.range, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) throw new EOFException; tokens = readln.split; } auto token = tokens[0]; tokens.popFront; return token; }
int readInt() { return readToken().to!int; }
long readLong() { return readToken().to!long; }
real readReal() { return readToken().to!real; }

void chmin(T)(ref T t, in T f) { if (t > f) t = f; }
void chmax(T)(ref T t, in T f) { if (t < f) t = f; }

int binarySearch(T)(in T[] as, in bool delegate(T) test) { int low = -1, upp = cast(int)(as.length); for (; low + 1 < upp; ) { int mid = (low + upp) >> 1; (test(as[mid]) ? low : upp) = mid; } return upp; }
int lowerBound(T)(in T[] as, in T val) { return as.binarySearch((T a) => (a < val)); }
int upperBound(T)(in T[] as, in T val) { return as.binarySearch((T a) => (a <= val)); }


immutable INF = 10L^^18;

long B;
int N;
long[] C;

void main() {
  try {
    for (; ; ) {
      B = readLong();
      N = readInt();
      C = new long[N];
      foreach (i; 0 .. N) {
        C[i] = readLong();
      }
      
      long ans = INF;
      void check(long target) {
        long cost;
        foreach (i; 0 .. N) {
          cost += abs(target - C[i]);
        }
        chmin(ans, cost);
      }
      
      const lim = (B + C.sum) / N;
      check(0);
      check(lim);
      foreach (i; 0 .. N) {
        if (C[i] <= lim) {
          check(C[i]);
        }
      }
      writeln(ans);
    }
  } catch (EOFException e) {
  }
}