I've read it for 15 min..AC at the first time...
sort all the integer to a descending sequence.
repeat for n-1 times:
combine a[1] and a[2](2sqrt(xy))
delete(a[1],a[2])
insert the new real number into the sequence
and remember to keep the descending.

print the final a[1].

what's mean here is delete(a[1],a[2]); don't understand

Hi Ayubxon,
             delete means "no longer worry about a[1] and a[2]".
You may not actually delete the values from array.

Regards
Anupam

Thanks