Editing 2019 Dec Bronze Problem 1 Cow Gymnastics (section)

==Problem Statement==

Cow Gymnastics is a USACO problem from the December 2020 contest.

The problem statement is as follows:

Farmer John has N cows (1 ≤ N ≤ 100,000) that he wants to train for a gymnastics competition. Each cow i has a skill level Si (1 ≤ Si ≤ 1,000,000,000).

FJ has M exercises (1 ≤ M ≤ 100,000) that he can use to train his cows. Each exercise j has a difficulty level Dj (1 ≤ Dj ≤ 1,000,000,000).

FJ wants to assign each cow to exactly one exercise. He wants to maximize the total skill level of all cows, but he also wants to make sure that the total difficulty of the exercises assigned to his cows is as small as possible.

Help FJ determine the maximum total skill level of his cows that can be achieved.