#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint1000000007;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000000000000
	

int main(){	
	
	long long B;
	cin>>B;
	int N;
	cin>>N;
	
	vector<long long> c(N);
	rep(i,N)cin>>c[i];
	sort(c.begin(),c.end());
	long long ans = Inf;
	long long ng = c[N/2]+1,ok = -1;
	while(ng-ok>1LL){
		long long mid = (ok+ng)/2;
		long long b = B;
		long long s= 0LL;
		rep(i,N){
			s += abs(mid-c[i]);
			b += c[i]-mid;
		}
		if(b>=0){
			ok = mid;
			ans = min(ans,s);
		}
		else{
			ng = mid;
		}
		
	}
	
	cout<<ans<<endl;
	
	return 0;
	
}