#include <iostream>
#include <vector>
#include <algorithm>

int main() {
	std::cin.tie(0);
	std::ios::sync_with_stdio(false);
	int b;
	std::cin >> b;
	int n;
	std::cin >> n;
	long long sum = 0;
	std::vector<int> c;
	int a;
	for (int i = 0; i < n; ++i) {
		std::cin >> a;
		c.push_back(a);
		sum += a;
	}
	std::sort(c.begin(), c.end());
	if (n == 1) {
		std::cout << "0" << std::endl;
		return 0;
	}
	long long count = 0, t = 20000000000;
	int lv, i;
	for (i = 0; i < n; ++i, t = count, count = 0) {
		for (int j = 0; j < n; ++j) {
			count += abs(c[i] - c[j]);
		}
		if (count >= t) {
			lv = c[i-1];
			break;
		}
	}
	if (i > n) {
		lv = c[n - 1];
	}
	int sa;
	if ((sa = lv * n - (sum + b)) > 0) {
		lv -= sa / n;
		lv -= ((sa % n) ? 1 : 0);
	}
	t = 0;
	for (int i = 0; i < n; ++i) {
		t += abs(lv - c[i]);
	}
	std::cout << t << std::endl;
}