B. XY Sequencetime limit per test2 secondsmemory limit per test256 megabytesinputstandard inputoutputstandard outputYou are given four integers n, B, x and y. You should build a sequence a_0, a_1, a_2, \dots, a_n where a_0 = 0 and for each i \ge 1 you can choose:   either a_i = a_{i - 1} + x  or a_i = a_{i - 1} - y. Your goal is to build such a sequence a that a_i \le B for all i and \sum\limits_{i=0}^{n}{a_i} is maximum possible.InputThe first line contains a single integer t (1 \le t \le 10^4) — the number of test cases. Next t cases follow.The first and only line of each test case contains four integers n, B, x and y (1 \le n \le 2 \cdot 10^5; 1 \le B, x, y \le 10^9).It's guaranteed that the total sum of n doesn't exceed 2 \cdot 10^5.OutputFor each test case, print one integer — the maximum possible \sum\limits_{i=0}^{n}{a_i}.ExampleInput
3
5 100 1 30
7 1000000000 1000000000 1000000000
4 1 7 3
Output
15
4000000000
-10
NoteIn the first test case, the optimal sequence a is [0, 1, 2, 3, 4, 5].In the second test case, the optimal sequence a is [0, 10^9, 0, 10^9, 0, 10^9, 0, 10^9].In the third test case, the optimal sequence a is [0, -3, -6, 1, -2].
3
5 100 1 30
7 1000000000 1000000000 1000000000
4 1 7 3

15 4000000000 -10 
['greedy', '*800']