Could anyone tell me why it WA#2?


program p1510_Use_QSort;

var
  d:array[1..500000]of longint;
  n,i,j,max,maxh:longint;

procedure qsort(s,t:longint);
  var
    i,j,p:longint;
  begin
  //make it randomize
    p:=random(t-s)+s+1;
    d[s]:=d[s] xor d[p];
    d[p]:=d[s] xor d[p];
    d[s]:=d[s] xor d[p];
  //start sort
    i:=s;j:=t;
    while true do begin
      while (i<j)and(d[i]<=d[j]) do dec(j);
      if i=j then break;
      d[i]:=d[i] xor d[j];d[j]:=d[i] xor d[j];d[i]:=d[i] xor d[j];
      while (i<j)and(d[i]<=d[j]) do inc(i);
      if i=j then break;
      d[i]:=d[i] xor d[j];d[j]:=d[i] xor d[j];d[i]:=d[i] xor d[j];
    end;
    dec(i);inc(j);
    if s<i then qsort(s,i);
    if j<t then qsort(j,t);
  end;

begin
  readln(n);
  for i:=1 to n do read(d[i]);
  randomize;
  qsort(1,n)
  writeln(d[n shr 1+1]);
end.