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

typedef long long ll;
#define rep(i,n) for(int i=0;i<(n);++i)
#define each(itr,c) for(__typeof(c.begin()) itr=c.begin(); itr!=c.end(); itr++)
#define mp make_pair
#define pb push_back
#define fi first
#define sc second

long ab(long p){
  return (p>0)?p:-p;
}

int main(int argc, char const *argv[]) {
  long b;
  int n;
  cin >>b >>n;

  std::vector<long> c(n);
  long sum=0;
  rep(i,n){
    cin >>c[i];
    sum+=c[i];
  }
  sort(c.begin(), c.end());

  long each=sum/n;

  long ans=0;
  rep(i,n) ans+=ab(c[i]-each);

  if((sum+b)/n>=each+1){
    long tmp=0;
    rep(i,n) tmp+=ab(c[i]-(each+1));
    ans=min(ans,tmp);
  }

  std::cout << ans << std::endl;
  return 0;
}