$1$ Profits

A shopkeeper has the option to buy $N$ items from the producer, the $i^a$ of which costs cost $i.$ He can sell the $i^{th}$ item at sell $i,$ Initially, he has $K$ rupees and $0$ items in his shop. At any moment his store can accommodate at most $1$ item, which means he has to sell the previous item before buying the next one from the producer.

What is the maximum profit he can achieve?

Notes

He can buy and sell any number of items.

He can use the profit previously earned to buy new items.

One item can be bought and sold atmost once.

Items can be bought and sold in any order and not necessarily in the order given as input.

Function description :

Complete the function solution$()$ provided in the editor. The function takes the following $4$ parameters and returns the solution:

$N.$ Represents the number of items

$.$ Represents the initial amount

cost: Represents the cost price of items

selt. Represents the selling price of items

Input format for custom testing

Note: Use this input format if you are testing against custom input or writing code in a language where we don't provide boilerplate code

The first line contains $N$ denoting the number of items.

The second line contains $K$ denoting the initial amount.

The third line contains cost denoting the cost price of items.

The fourth line contains sell denoting the selling price of items.

Output format

Print an integer, rebresenting the maximum total profit: