#include <string>
#include <vector>
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<stack>
#include<queue>
#include<cmath>
#include<algorithm>
#include<functional>
#include<list>
#include<deque>
#include<bitset>
#include<set>
#include<map>
#include<unordered_map>
#include<cstring>
#include<sstream>
#include<complex>
#include<iomanip>
#include<numeric>
#define X first
#define Y second
#define pb push_back
#define rep(X,Y) for (int (X) = 0;(X) < (Y);++(X))
#define rrep(X,Y) for (int (X) = (Y-1);(X) >=0;--(X))
#define repe(X,Y) for ((X) = 0;(X) < (Y);++(X))
#define peat(X,Y) for (;(X) < (Y);++(X))
#define all(X) (X).begin(),(X).end()
#define rall(X) (X).rbegin(),(X).rend()

using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
template<class T> using vv=vector<vector<T>>;
template<class T> ostream& operator<<(ostream &os, const vector<T> &t) {
os<<"{"; rep(i,t.size()) {os<<t[i]<<",";} os<<"}"<<endl; return os;}
template<class S, class T> ostream& operator<<(ostream &os, const pair<S,T> &t) { return os<<"("<<t.first<<","<<t.second<<")";}
ll INF=1e12;
ll solve(int m,ll b,vector<ll> &c){
  ll n=c.size(),re=0;
  rep(i,n){
    if(c[i]>m){
      re+=c[i]-m;
      b+=c[i]-m;
    }
    if(c[i]<m){
      re+=m-c[i];
      b-=m-c[i];
    }
  }
  return b<0?INF:re;
}

int main(){
  ios_base::sync_with_stdio(false);
  cout<<fixed<<setprecision(0);
  int i,j,k;
  ll b,n;
  cin>>b>>n;
  vector<ll> c(n);
  rep(i,n)
    cin>>c[i];
  ll re,ave=accumulate(all(c),b)/n;
  re=solve(ave,b,c);
  rep(i,n)
    re=min(re,solve(c[i],b,c));
  cout<<re<<endl;
  return 0;
}