Problem:
Score : 100 points

Problem Statement

In this problem, you should process T testcases.

For each testcase, you are given four integers N, M, A, B.

Calculate \sum_{i = 0}^{N - 1} floor((A \times i + B) / M).

Constraints

1 \leq T \leq 100,000

1 \leq N, M \leq 10^9

0 \leq A, B < M

Input

Input is given from Standard Input in the following format:

T
N_0 M_0 A_0 B_0
N_1 M_1 A_1 B_1
:
N_{T - 1} M_{T - 1} A_{T - 1} B_{T - 1}

Output

Print the answer for each testcase.

Sample Input 1

5
4 10 6 3
6 5 4 3
1 1 0 0
31415 92653 58979 32384
1000000000 1000000000 999999999 999999999

Sample Output 1

3
13
0
314095480
499999999500000000

Solution in Rust (1.42.0) (judge verdict: Accepted)

#![doc = " # Bundled libraries"]
#![doc = ""]
#![doc = " ## `kyopro_lib` (private)"]
#![doc = ""]
#![doc = " ### Modules"]
#![doc = ""]
#![doc = " - `::__kyopro_lib::math` → `$crate::math`"]
#[allow(unused_imports)]
use itertools::Itertools;
use proconio::input;
#[allow(unused_imports)]
use proconio::marker::*;
fn main() {
    input! { t : usize , nmab : [(i64 , i64 , i64 , i64) ; t] , }
    for (n, m, a, b) in nmab {
        println!("{}", math::floor_sum(n, m, a, b));
    }
}
pub mod math {
    pub fn floor_sum(n: i64, m: i64, mut a: i64, mut b: i64) -> i64 {
        let mut res = 0;
        res += b / m * n;
        b %= m;
        res += a / m * n * (n - 1) / 2;
        a %= m;
        let y_max = (n * a + b) / m;
        if y_max == 0 {
            return res;
        }
        let x_max = y_max * m - b;
        res + (n - (x_max + a - 1) / a) * y_max + floor_sum(y_max, a, m, (a - x_max % a) % a)
    }
}