What is the trick of problem 7?
I tried a file of 250000 numbers 2^31-1 and got the answer 2147483647.0
So this is right.
I tried 1 0 and got 0.0
There was no TLE but a wrong answer.

This is a piece of my code
Something is still wrong

CreatePQueue(a);              // creates a priority queue
readln(N);
for i:=1 to (N div 2) + 1 do
begin
  readln(j);
  PriorityEnq(a,j);           //push the number
end;
for i:= (N div 2) + 2 to N do
begin
  readln(j);
  PriorityEnq(a,j);          //push the number
  PriorityDeq(a,k);          //pop the greatest
end;
if odd(N) then
begin
  PriorityDeq(a,k);         //pop the gratest
  s:=k;
  writeln(s:0:1);
end
else
begin
  PriorityDeq(a,l);
  PriorityDeq(a,k);
  s:=l+k;
  writeln(s/2:0:1);
end;