1 #include <iostream>
 2 #include <stdio.h>
 3 #include <math.h>
 4 #include <iomanip> 
 5 #include <algorithm>
 6  
 7 using namespace std;
 8 
 9 int n;
10 double w[103];
11 
12 int main() {
13     double res = 0;
14     scanf("%d", &n);
15     for (int i = 0; i < n; i++) {
16         scanf("%lf", &w[i]);
17     }
18     while (n > 0) {   
19         if (n == 1) {
20             res = w[0];
21             break;
22         }     
23         
24         sort(w, w + n);
25         double newW = 2 * sqrt(w[n - 1] * w[n - 2]);
26         res = newW;
27  
28         w[n - 2] = newW;
29         n--;
30     }
31     
32     cout << setiosflags(ios::fixed) << setprecision(3) << res << endl;
33     return 0;
34 }