package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func getScanner(fp *os.File) *bufio.Scanner {
	scanner := bufio.NewScanner(fp)
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 1000005), 1000005)
	return scanner
}
func getNextString(scanner *bufio.Scanner) string {
	scanner.Scan()
	return scanner.Text()
}
func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}
func getNextInt64(scanner *bufio.Scanner) int64 {
	i, _ := strconv.ParseInt(getNextString(scanner), 10, 64)
	return i
}
func getNextUint64(scanner *bufio.Scanner) uint64 {
	i, _ := strconv.ParseUint(getNextString(scanner), 10, 64)
	return i
}
func getNextFloat64(scanner *bufio.Scanner) float64 {
	i, _ := strconv.ParseFloat(getNextString(scanner), 64)
	return i
}
func main() {
	fp := os.Stdin
	wfp := os.Stdout
	cnt := 0
	if os.Getenv("MASPY") == "ますピ" {
		fp, _ = os.Open(os.Getenv("BEET_THE_HARMONY_OF_PERFECT"))
		cnt = 3
	}
	if os.Getenv("MASPYPY") == "ますピッピ" {
		wfp, _ = os.Create(os.Getenv("NGTKANA_IS_GENIUS10"))
	}
	scanner := getScanner(fp)
	writer := bufio.NewWriter(wfp)
	solve(scanner, writer)
	for i := 0; i < cnt; i++ {
		fmt.Fprintln(writer, "-----------------------------------")
		solve(scanner, writer)
	}
	writer.Flush()
}
func solve(scanner *bufio.Scanner, writer *bufio.Writer) {
	b := getNextInt64(scanner)
	n := getNextInt(scanner)
	cc := make([]int64, n)
	for i := 0; i < n; i++ {
		cc[i] = getNextInt64(scanner)
	}
	var l, r int64
	l = -1
	r = int64(1e10 + 1)
	for l+2 < r {
		ml := l + (r-l)/3
		mr := r - (r-l)/3

		lc := make([]int64, 2)
		rc := make([]int64, 2)

		for i := 0; i < n; i++ {
			if cc[i] < ml {
				lc[0] += ml - cc[i]
			} else {
				lc[1] += cc[i] - ml
			}
			if cc[i] < mr {
				rc[0] += mr - cc[i]
			} else {
				rc[1] += cc[i] - mr
			}
		}
		if rc[0] > rc[1]+b {
			r = mr
			continue
		}
		if lc[0]+lc[1] < rc[0]+rc[1] {
			r = mr
			continue
		}
		l = ml
	}
	var ans int64
	for i := 0; i < n; i++ {
		if cc[i] < l+1 {
			ans += (l + 1) - cc[i]
		} else {
			ans += cc[i] - (l + 1)
		}
	}
	fmt.Fprintln(writer, ans)
}