#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
//using LL = __int128
ll n, a[1111];
ld dp[1111][1111], dis[1111][1111], f[1111][1111];
int main(){
	scanf("%lld", &n);
	for(int i = 1 ; i <= 2 * n ; i++){
		scanf("%lld", a + i);
	}
	sort(a + 1, a + 1 + 2 * n);
	for(int i = 1 ; i <= 2 * n ; i++)
		for(int j = i + 1 ; j <= 2 * n ; j++){
			dis[i][j] = sqrt(a[j] - a[i]);
			//printf("%.10Lf%c", dis[i][j], " \n"[j == 2 * n]);
		}
	for(int len = 2 ; len <= 2 * n ; len += 2){
		for(int i = 1 ; i + len - 1 <= 2 * n ; i++){
			int l = i, r = i + len - 1;
			dp[l][r] = dis[l][r] + dp[l + 1][r - 1];
			for(int i = l + 2 ; i <= r - 2 ; i += 2)
				dp[l][r] = min(dp[l][r], dis[l][r] + dp[l + 1][i] + dp[i + 1][r - 1]);
		}
	}
	//*
	for(int i = 1 ; i <= 2 * n ; i++)
		for(int j = 1 ; j <= 2 * n ; j++)
			f[i][j] = 1e10;
	//*/
	for(int len = 2 ; len <= 2 * n ; len += 2){
		for(int i = 1 ; i + len - 1 <= 2 * n ; i++){
			int l = i, r = i + len - 1;
			f[l][r] = min(dp[l][r], dis[l][r] + f[l + 1][r - 1]);
			for(int i = l + 1 ; i <= r - 1 ; i += 2){
				f[l][r] = min(f[l][r], f[l][i] + f[i + 1][r]);
				//cout << l << " " << r << " " << f[l][r] << "\n";
			}
		}
	}
	/*
	ld ans = dp[1][2 * n];
	for(int i = 2 ; i < 2 * n ; i += 2){
		printf("%.10Lf %.10Lf %.10Lf\n", ans, dp[1][i], dp[i + 1][2 * n]);
		ans = min(ans, dp[1][i] + dp[i + 1][2 * n]);
	}
	printf("%.10Lf\n", ans);
	//*/
	printf("%.10Lf\n", f[1][2 * n]);
	return 0;
}