#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <math.h>
#include <cmath>
#include <limits.h>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <functional>
#include <stdio.h>
using namespace std;

long long MOD = 1000000007;

int main() {
    
    long long B;
    cin >> B;
    int N;
    cin >> N;
    vector<long long> A(N);
    long long s = B;
    for ( int i = 0; i < N; i++ ) {
        cin >> A[i];
        s += A[i];
    }
    sort( A.begin(), A.end() );

    long long m = A[ N%2==0 ? N/2 -1 : N/2 ];

    long long x = ( s >= m*N ) ? m : s/N;
    
    long long ans = 0;
    for ( int i = 0; i < N; i++ ) {
        ans += abs(A[i]-x);
    }
    cout << ans << endl;

    return 0;
}