#define _USE_MATH_DEFINES

#include <iostream>
#include <iomanip>

#include <algorithm>
#include <cmath>

#include <string>
#include <list>
#include <queue>
#include <vector>
#include <complex>
#include <set>

/////////
#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i,n) REP(i,0,n)
#define P(p) cout<<(p)<<endl;
/////////
typedef long long LL;
typedef long double LD;
/////////
using namespace::std;
/////////

LL B,N;
LL C[10],Csum=0;

LL solve(LL aveP){
	LL ans=0;
	for(int k=0;k<N;++k){
		if( C[k] < aveP){
			ans += aveP - C[k];
		}else{
			ans += C[k] - aveP;
		}
	}
	return ans;
}
int main(void){
    std::cin.tie(0); 
    std::ios::sync_with_stdio(false);
    std::cout << std::fixed;//
    //cout << setprecision(6);//
    
	cin>>B>>N;
	
	rep(i,N){
		cin>>C[i];
		Csum += C[i];
	}
	sort(C,C+N);

	LL aveMax = (Csum+B)/N;
	LL aveMin = C[0];

	LL leftSol = solve(aveMin);
	LL topSol  = solve(aveMax);
	LL midSol;
	LL left = aveMin;
	LL top  = aveMax;
	LL mid;
	while(top-left>1){
		mid = (top+left)/2;
		midSol = solve(mid);
		if(leftSol > midSol){
			left = mid;
			leftSol = midSol;
		}
		else if(leftSol < midSol){
			top = mid;
			topSol = midSol;
		}else{
			top = mid;
			topSol = midSol;
		}
	}
	P(min(leftSol,topSol));
    return 0;
}