Tudor is buying ~N~ blocks of cheese. Each block of cheese has a regular price and a discounted price.

Tudor has ~K~ coupons that allow him to buy a block of cheese for the discounted price instead of the regular price. Each coupon can be used for exactly one block of cheese.

Given that Tudor wants to buy all ~N~ blocks of cheese, compute the minimum amount of money he must spend.

Constraints

~1 \le N \le 10^5~

~0 \le K \le N~

~1 \le d_i \le p_i \le 10^9~

Input Specification

The first line contains two space separated integers, ~N~ and ~K~.

The next ~N~ lines each contain two space separated integers, ~p_i~ and ~d_i~ representing the regular price and discounted price of block ~i~, respectively.

Output Specification

Output the minimum amount of money Tudor must spend.

Sample Input

2 1
100 0
10 10

Sample Output

10