module main;
// https://roiti46.hatenablog.com/entry/2015/04/29/yukicoder_No.198_%E3%82%AD%E3%83%A3%E3%83%B3%E3%83%87%E3%82%A3%E3%83%BC%E3%83%BB%E3%83%9C%E3%83%83%E3%82%AF%E3%82%B9%EF%BC%92 より
// 三分探索
import std;

void main()
{
	// 入力
	long B = readln.chomp.to!long;
	int N = readln.chomp.to!int;
	auto C = new long[](N);
	foreach (ref c; C)
		c = readln.chomp.to!long;
	// 答えの計算
	long ans = 10L ^^ 18;
	long l = -1, r = 10L ^^ 18;
	while (r - l > 2) {
		long lm = (2 * l + r) / 3, rm = (l + 2 * r) / 3;
		if (C.map!(c => lm - c).sum > B)
			r = lm;
		else if (C.map!(c => rm - c).sum > B)
			r = rm;
		else if (C.map!(c => abs(lm - c)).sum <= C.map!(c => abs(rm - c)).sum)
			r = rm;
		else
			l = lm;
	}
	// 答えの出力
	writeln(C.map!(c => abs((r + l) / 2 - c)).sum);
}