Find the maximum achievable number

#[test]
fn t1() {
    let start = std::time::Instant::now();
    let val = Solution::the_maximum_achievable_x(4, 1);
    let expected = 6;
    log_result!(val == expected, "t1", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t2() {
    let start = std::time::Instant::now();
    let val = Solution::the_maximum_achievable_x(3, 2);
    let expected = 7;
    log_result!(val == expected, "t2", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t3() {
    let start = std::time::Instant::now();
    let val = Solution::the_maximum_achievable_x(1, 0);
    let expected = 1;
    log_result!(val == expected, "t3", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t4() {
    let start = std::time::Instant::now();
    let val = Solution::the_maximum_achievable_x(50, 50);
    let expected = 150;
    log_result!(val == expected, "t4", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t5() {
    let start = std::time::Instant::now();
    let val = Solution::the_maximum_achievable_x(1, 1);
    let expected = 3;
    log_result!(val == expected, "t5", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t6() {
    let start = std::time::Instant::now();
    let val = Solution::the_maximum_achievable_x(10, 5);
    let expected = 20;
    log_result!(val == expected, "t6", start, &expected, &val);
    assert_eq!(val, expected);
}