#include <bits/stdc++.h>
using namespace std;



vector<long long> A;
double f(double x){
	double cnt = 0;
	for(int i = 0 ; i < A.size() ; i++) cnt +=  fabs(A[i]-x);
	return -cnt;
}

double search(double left, double right)
{
	for (int loop = 0; loop < 1919; ++loop){
		if (f((left * 2 + right) / 3) > f((left + right * 2) / 3)){
			right = (left + right * 2) / 3;
		} else {
			left = (left * 2 + right) / 3;
		}
	}
	return (right + left) * 0.5;
}

int main(){
	long long B,N;
	cin >> B >> N;
	vector<long long> C(N);
	long long sum = B;
	for(int i = 0 ; i < N ; i++){
		cin >> C[i];
		sum += C[i];
	}
	::A = C;
	sum /= N;
	
	//cout << search(0,sum) << endl;
	//cout << f(720) << "<" << endl;
	
	cout << (long long)(-f(search(0,sum))+1e-9) << endl;
	
	
}