#include <iostream>
#include <vector>
#include <numeric>
#include <cmath>

using namespace std;

long long turns(long long targetCount, const vector<long long>& boxes) {
	long long result = 0;
	for (size_t i = 0; i < boxes.size(); ++i) {
		result += abs(boxes[i] - targetCount);
	}
	return result;
}

int main() {
	long long b;
	int n;
	cin >> b >> n;
	vector<long long> boxes(n);
	for (int i = 0; i < n; ++i) {
		cin >> boxes[i];
	}
	long long left = 0;
	long long right = (b + std::accumulate(boxes.begin(), boxes.end(), 0LL)) / boxes.size();
	while (left < right) {
		long long middleLeft = (2 * left + right) / 3;
		long long middleRight = (left + 2 * right + 2) / 3;
		if (turns(middleLeft, boxes) < turns(middleRight, boxes)) {
			right = middleRight - 1;
		} else {
			left = middleLeft + 1;
		}
	}
	cout << turns(left, boxes) << endl;
	return 0;
}