1.18. Exercise: Django

Dr. King Schultz and Django, as ruthless warriors of justice, are wandering around America and hunting down wanted criminals. There are n criminals they need to seize in total. For the first criminal they take down, they receive 100 U.S. Dollars. Afterwards, for each lawbreaker they apprehend, they are paid $100 more than the previous one. Namely; if they take down 3 criminals one by one, they are going to earn $100, $200 and $300 for the first, second and third one respectively. However, bullets are not cheap these days. One bullet costs \(m\) Dollars. They are brooding on how much they are going to profit, after wasting all those expensive bullets on filthy criminals.

Given n (in the first line) and m (in the second line) as input, can you find how much money they are going to earn? Obviously, since Django is an experienced sharpshooter, they will not use more than one bullet for one criminal.

Sample I/O:

Input:
4
50

Output:
800

Input:
5
72

Output:
1140