#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<cctype>
#include<cstdlib>
#include<algorithm>
#include<bitset>
#include<vector>
#include<list>
#include<deque>
#include<queue>
#include<map>
#include<set>
#include<stack>
#include<cmath>
#include<sstream>
#include<fstream>
#include<iomanip>
#include<ctime>
#include<complex>
#include<functional>
#include<climits>
#include<cassert>
#include<iterator>
#include<valarray>
//#include<bits/stdc++.h>
using namespace std;
int b;
int n;
vector<int> v;
long long int f(long long int a){
	long long int r = 0;
	for (int i = 0; i < v.size(); i++){
		r += abs(v[i] - a);
	}
	return r;
}
int main(){
	scanf("%d", &b);
	scanf("%d", &n);
	long long int mint = 0;
	long long int maxt = 0;
	for (int i = 0; i < n; i++){
		int a;
		scanf("%d", &a);
		v.push_back(a);
		maxt += a;
	}
	maxt += (long long int)(b);
	maxt /= (long long int)(n);
	while (mint + 2LL < maxt){
		long long int len = maxt - mint + 1LL;
		len /= 3;
		long long int mid = mint + len;
		long long int mid1 = mid + len;
		long long int v = f(mid);
		long long int vv = f(mid1);
		if (v > vv){
			mint = mid;
		}
		else{
			maxt =mid1;
		}
	}
	long long int ans = LLONG_MAX;
	for (long long int i = mint; i <= maxt; i++){
		ans = min(ans, f(i));
	}
	printf("%lld\n", ans);
	return 0;
}