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 hi. As Petya is older, he wants to take the chores with complexity larger than some value x (hi > x) to leave to Vasya the chores with complexity less than or equal to x (hi ≤ 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 Format: 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, ..., hn (1 ≤ hi ≤ 109), hi 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 Format: Print the required number of ways to choose an integer value of x. If there are no such ways, print 0. 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.