#include <bits/stdc++.h>
#define rep(i, a, n) for(int i = a; i < n; i++)
#define REP(i, n) rep(i, 0, n)
#define repb(i, a, b) for(int i = a; i >= b; i--)
#define all(a) a.begin(), a.end()
#define int long long
#define chmax(x, y) x = max(x, y)
#define chmin(x, y) x = min(x, y)
using namespace std;
typedef pair<int, int> P;
const int mod = 1000000007;
const int INF = 1e12;

signed main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin >> n;
    vector<double> a(n);
    rep(i, 0, n){
        cin >> a[i];
    }
    sort(all(a));
    double ans = 0;
    double mid = a[n / 2];
    if(n % 2 == 0) mid = (a[n / 2] + a[n / 2 - 1]) / 2.0;
    rep(i, 0, n){
        ans += fabs(mid - a[i]);
    }
    printf("%.10lf\n", ans);
}