Problem:
Score : 300 points

Problem Statement

Takahashi made N problems for competitive programming.
The problems are numbered 1 to N, and the difficulty of Problem i is represented as an integer d_i (the higher, the harder).

He is dividing the problems into two categories by choosing an integer K, as follows:

A problem with difficulty K or higher will be for ARCs.

A problem with difficulty lower than K will be for ABCs.

How many choices of the integer K make the number of problems for ARCs and the number of problems for ABCs the same?

Problem Statement

2 \leq N \leq 10^5

N is an even number.

1 \leq d_i \leq 10^5

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
d_1 d_2 ... d_N

Output

Print the number of choices of the integer K that make the number of problems for ARCs and the number of problems for ABCs the same.

Sample Input 1

6
9 1 4 4 6 7

Sample Output 1

2

If we choose K=5 or 6, Problem 1, 5, and 6 will be for ARCs, Problem 2, 3, and 4 will be for ABCs, and the objective is achieved.
Thus, the answer is 2.

Sample Input 2

8
9 1 14 5 5 4 4 14

Sample Output 2

0

There may be no choice of the integer K that make the number of problems for ARCs and the number of problems for ABCs the same.

Sample Input 3

14
99592 10342 29105 78532 83018 11639 92015 77204 30914 21912 34519 80835 100000 1

Sample Output 3

42685

Solution in Pascal (FPC 2.6.2) (judge verdict: Accepted)

var n,re,t,i:longint;
    a:array[1..100000] of longint;


procedure sort(l,r:longint);
var x,tmp,i,j:longint;
begin
	i:=l; j:=r;
	x:=a[(l + r) shr 1];
	repeat
	  while a[i] < x do inc(i);
	  while a[j] > x do dec(j);
	  if i <= j then
	    begin
	      tmp:=a[i];
	      a[i]:=a[j];
	      a[j]:=tmp;
	      inc(i);
	      dec(j);
	    end;
	until i > j;
	if l < j then sort(l,j);
	if i < r then sort(i,r);
end;

begin
	readln(n);
	for i:=1 to n do read(a[i]);
	sort(1,n);
    t:= n shr 1;
    if a[t] = a[t + 1] then re:=0
    else re:=a[t + 1] - a[t];
    write(re);
end.