#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;

long long int b;
int n;
unsigned int randxor()
{
	static unsigned int x = 123456789, y = 362436069, z = 521288629, w = 88675123;
	unsigned int t;
	t = (x ^ (x << 11)); x = y; y = z; z = w; return(w = (w ^ (w >> 19)) ^ (t ^ (t >> 8)));
}
vector<long long int> v;
long long int countt(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("%lld", &b);
	scanf("%d", &n);
	long long int mint = 0;
	long long int maxt = 0;
	for (int i = 0; i < n; i++){
		long long int a;
		scanf("%lld", &a);
		v.push_back(a);
		maxt += a;
	}
	mint = countt(maxt / n);
	maxt += b;
	maxt /= (long long int)(n);
	mint = min(mint, countt(maxt));
	while (clock() / (double)(CLOCKS_PER_SEC) < 0.95){
		mint = min(mint, countt(rand() % (maxt + 1LL)));
	}
	printf("%lld\n", mint);
	return 0;
}