## Lunch Choice

Points: 1
Time limit: 1.0s
Memory limit: 256M

Author:
Problem type
Allowed languages
C, C++, Java, Python

While furiously programming the donation site for the Cameron Hall 2020 Charity UnVigil (https://charityunvigil.online/) James and Felix decide to have a lunch break. Being extremely hard workers they give themselves exactly $$k$$ units of time to have lunch.

They have a list of $$n$$ venues. The $$i$$-th venue is characterized by two integers $$f_i$$ and $$t_i$$. $$t_i$$ is the time needed to lunch at the $$i$$-th venue. If $$t_i$$ exceeds $$k$$ then James and Felix's joy will equal $$f_i - (t_i - k)$$. Otherwise they get exactly $$f_i$$ units of joy.

Your task as the omniscient narrator is to choose the best place to have lunch maximizing joy (which may not be positive).

#### Input Specification

The first line contains two space-separated integers $$n (1 \leq n \leq 10^4)$$ and $$k(1 \leq k \leq 10^9)$$; the number of venues and time they give themselves respectively. Each of the next $$n$$ lines contains two space-separated integers $$f_i (1 \leq f_i \leq 10^9)$$ and $$t_i (1 \leq t_i \leq 10^9)$$, the characteristics of the $$i$$-th venue.

#### Output Specification

A single integer, the maximum joy that James and Felix can get from their lunch.

#### Sample Input 1

2 5
3 3
4 5

#### Sample Output 1

4

#### Sample Input 2

4 6
5 8
3 6
2 3
2 2

#### Sample Output 2

3

#### Sample Input 3

1 5
1 7

#### Sample Output 3

-1