Buying Sweets

There are $N$ sweets in the store. The cost of the $i^{th}$ sweet is $A_i$ rupees. Chef is a regular customer, so **after** buying the $i^{th}$ sweet, he gets a **cashback** of $B_i$ rupees. Chef has $R$ rupees. He is fond of all the sweets, so he wants you to calculate the maximum number of sweets he can buy. Note that he can buy the same type of sweet multiple times, as long as he has the money