use std::io::*;
use std::cmp;

fn main() {
	let mut s = String::new();
	std::io::stdin().read_to_string(&mut s).ok();
	let mut itr = s.trim().split_whitespace();
	let b: isize = itr.next().unwrap().parse().unwrap();
	let n: usize = itr.next().unwrap().parse().unwrap();
	let mut c: Vec<isize> = itr.map(|e| e.parse().unwrap()).collect();
	c.sort();
	
	let med = 
		if n % 2 == 0 { (c[n / 2] + c[n / 2 - 1]) / 2 }
		else { c[n / 2] };

	let s: isize = c.iter().sum();
	let x = cmp::min((b + s) / n as isize , med);

	let mut ans = 0;
	for i in 0..n { ans += (x - c[i]).abs(); }
	
	println!("{}", ans);
}