#include <cstdio>
#include <cstring>
#include <cmath>
#include <cassert>
#include <random>
#include <vector>
#include <algorithm>
#include <array>
#include <functional>
#include <utility>
#include <regex>
#include <tuple>
#include <map>
#include <set>
#include <iostream>

using namespace std;

int main(){
	int b,n;
	-scanf("%d%d",&b,&n);
	vector<int> c(n);
	int64_t sum=b,average,step=0,minstep=0x7fffffffffffffffL;
	for(auto &i:c){
		-scanf("%d",&i);
		sum+=i;
	}
	average=sum/n;
	for(auto &i:c){
		if(i>average){
			step+=i-average;
			b+=i-average;
			i=average;
		}
	}
	auto calcstep=[](vector<int> t,int target,int b){
		int64_t step=0;
		for(int i:t){
			step+=abs(target-i);
			b+=target-i;
		}
		return b>=0?step:0x7fffffffffffffffL;
	};
	auto t=calcstep(c,c[c.size()/2],b);
	minstep=min(minstep,t);
	printf("%ld\n",step+minstep);
	return 0;
}