var a:array[1..100] of longint;
    n,i,j:longint;
    max:extended;

begin
 readln(n);
 max:=0;
 for i:=1 to n do
   begin
     readln(a[i]);
     for j:=1 to i-1 do
      if sqrt(a[j]*a[i])>max then max:=sqrt(a[j]*a[i])
   end;
 writeln((max*2):0:2);
end.

No. Your program finds the maximal value of a[i]*a[j]. Your task is
different.

Let you have n numbers: a[1],...,a[n]. You can change any two numbers
a[i], a[j] with 2*sqrt(a[i],a[j]). So you've got another sequence : b
[1],...,b[n-1], where

b[1]=a[1];
...
b[i-1]=a[i-1];
b[i]=2*sqrt(a[i],a[j]);
b[i+1]=a[i+1];
...
b[j-1]=a[j-1];
b[j]=a[j+1];
...
b[n-1]=a[n].

Repeat procedure until you'll get the only integer.
You are to find the minimal value of this number.

Good luck!

Its solution is not correct!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!