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

#define QwQ3301AwA return 0
#define ll long long

int n;
int a[1000];
double f[805][805];
bool vis[805][805];

double dfs(int l, int r) {
	if (l > r) return 0;
	if (l + 1 == r) return sqrt(a[r] - a[l]);
	if (vis[l][r]) return f[l][r];
	vis[l][r] = 1;
	f[l][r] = 1e14;
	for (int k = r - 1; k >= l; k -= 2) {
		f[l][r] = min(f[l][r], dfs(l, k - 1) + dfs(k + 1, r - 1) + sqrt(a[r] - a[k]));
	}
	return f[l][r];
}

signed main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	cin >> n;
	for (int i = 1; i <= 2 * n; i++) cin >> a[i];
	sort(a + 1, a + 2 * n + 1);
	printf("%.10lf", dfs(1, 2 * n));
	QwQ3301AwA;
}