import java.util.*;

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