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

long long solve(const vector<int> c, long long x)
{
    int n = c.size();
    long long ans = 0;
    for(int i=0; i<n; ++i)
        ans += abs(c[i] - x);
    return ans;
}

int main()
{
    int b, n;
    cin >> b >> n;
    vector<int> c(n);
    for(int i=0; i<n; ++i)
        cin >> c[i];

    long long left = 0;
    long long right = (accumulate(c.begin(), c.end(), 0LL) + b) / n;
    while(right - left > 5){
        long long mid1 = (left * 2 + right) / 3;
        long long mid2 = (left + right * 2) / 3;

        long long p = solve(c, mid1);
        long long q = solve(c, mid2);
        if(p < q)
            right = mid2;
        else
            left = mid1;
    }

    long long ans = LLONG_MAX;
    for(long long i=left; i<=right; ++i)
        ans = min(ans, solve(c, i));
    cout << ans << endl;

    return 0;
}