Problem Statement
Alia has to buy n dresses, so she decides to shop from Myntra. She Found that there is sale on dresses on Myntra. This sale will lasts for next one month. The price of a dress is ai $ now and it will become bi $ after one month of sale.
As myntra sellers can be dishonest so some dresses could be more expensive now than after a month of sale.
Alia decided to buy at least x of dresses now, but wait with the rest of the month in order to save money as much as possible. Your task is to determine the minimum dollars that Alia can spend to buy all n dresses.
Input
First line contains two positive integers n and x (1 ≤ n ≤ 2·105, 0 ≤ x≤ n) — total number of dresses Alia has to buy and minimal number of dresses Alia wants to buy right now.
Second line contains sequence of integers a1, a2, ..., an (1 ≤ ai ≤ 104) — prices of dresses during sale (i.e. right now).
Third line contains sequence of integers b1, b2, ..., bn (1 ≤ bi ≤ 104) — prices of dresses after sale (i.e. after a month).
Output
Print the minimal dollars Alia will spend to buy all n dresses. Remember, she should buy at least x dresses right now.
Alia should buy dresses 1, 2, 4 and 5 right now, paying for them 3, 4, 10 and 3, respectively. She should buy dress 3 after a month of sale, she will pay 5$ for it. In total she will spend 3 + 4 + 10 + 3 + 5 = 25$.