#include<bits/stdc++.h>
using namespace std;
#define REP(i,n) for(int i=0;i<n;i++)
#define ll long long

int main(){
    int b,n;
    ll ans=0,l,ave=0;
    cin >> b >> n;
    vector<int> c(n);
    REP(i,n) cin >> c[i],ave+=c[i];
    ave+=b;ave/=n;
    sort(c.begin(),c.end());
    if(n%2!=0) l=c[n/2];
    else l=(c[n/2-1]+c[n/2])/2;
    l=min(ave,l);
    REP(i,n) ans+=abs(l-c[i]);
    cout << ans << endl;
    return 0;
}