Chores

2000ms

262144K

Description:

Petya and Vasya are brothers. Today is a special day for them as their parents left them home alone and commissioned them to do n chores. Each chore is characterized by a single parameter — its complexity. The complexity of the i-th chore equals h_i.

As Petya is older, he wants to take the chores with complexity larger than some value x (h_i > x) to leave to Vasya the chores with complexity less than or equal to x (h_i ≤ x). The brothers have already decided that Petya will do exactly a chores and Vasya will do exactly b chores (a + b = n).

In how many ways can they choose an integer x so that Petya got exactly a chores and Vasya got exactly b chores?

Input:

The first input line contains three integers n, a and b (2 ≤ n ≤ 2000; a, b ≥ 1; a + b = n) — the total number of chores, the number of Petya's chores and the number of Vasya's chores.

The next line contains a sequence of integers h₁, h₂, ..., h_n (1 ≤ h_i ≤ 10⁹), h_i is the complexity of the i-th chore. The numbers in the given sequence are not necessarily different.

All numbers on the lines are separated by single spaces.

Output:

Print the required number of ways to choose an integer value of x. If there are no such ways, print 0.

Sample Input:

5 2 3
6 2 3 100 1

Sample Output:

Sample Input:

7 3 4
1 1 9 1 1 1 1

Sample Output:

Note:

In the first sample the possible values of x are 3, 4 or 5.

In the second sample it is impossible to find such x, that Petya got 3 chores and Vasya got 4.

Informação

Provedor Codeforces

Código CF169A