package no198;

import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int b = sc.nextInt();
		int n = sc.nextInt();
		long sum = b;
		int[] c = new int[n];
		for(int i=0;i<n;i++) {
			c[i] = sc.nextInt();
			sum += c[i];
		}
		Arrays.sort(c);
		long x = c[(n-1)/2];
		if (x * n > sum) {
			x = sum / n;
		}
		long ans = 0;
		for(int i=0;i<n;i++) {
			ans += Math.abs(c[i] - x);
		}
		System.out.println(ans);
	}
}