#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
typedef long long LL;
int main(){
	int b, n; cin >> b >> n;
	vector<int> c(n);
	LL sum = b;
	for (int i = 0; i < n; i++){
		cin >> c[i];
		sum += c[i];
	}
	sort(c.begin(), c.end());
	int t = min((int)(sum / n), c[n / 2]);
	LL ans = 0;
	for (int ci : c){ ans += abs(ci - t); }
	cout << ans << endl;
	return 0;
}