CF1238B.Kill 'Em All

Ivan plays an old action game called Heretic. He's stuck on one of the final levels of this game, so he needs some help with killing the monsters.

The main part of the level is a large corridor (so large and narrow that it can be represented as an infinite coordinate line). The corridor is divided into two parts; let's assume that the point $x = 0$ is where these parts meet.

The right part of the corridor is filled with $n$ monsters — for each monster, its initial coordinate $x_i$ is given (and since all monsters are in the right part, every $x_i$ is positive).

The left part of the corridor is filled with crusher traps. If some monster enters the left part of the corridor or the origin (so, its current coordinate becomes less than or equal to $0$), it gets instantly killed by a trap.

The main weapon Ivan uses to kill the monsters is the Phoenix Rod. It can launch a missile that explodes upon impact, obliterating every monster caught in the explosion and throwing all other monsters away from the epicenter. Formally, suppose that Ivan launches a missile so that it explodes in the point $c$. Then every monster is either killed by explosion or pushed away. Let some monster's current coordinate be $y$, then:

• if $c = y$, then the monster is killed;
• if $y \lt c$, then the monster is pushed $r$ units to the left, so its current coordinate becomes $y - r$;
• if $y \gt c$, then the monster is pushed $r$ units to the right, so its current coordinate becomes $y + r$.

Ivan is going to kill the monsters as follows: choose some integer point $d$ and launch a missile into that point, then wait until it explodes and all the monsters which are pushed to the left part of the corridor are killed by crusher traps, then, if at least one monster is still alive, choose another integer point (probably the one that was already used) and launch a missile there, and so on.

What is the minimum number of missiles Ivan has to launch in order to kill all of the monsters? You may assume that every time Ivan fires the Phoenix Rod, he chooses the impact point optimally.

You have to answer $q$ independent queries.

伊万正在玩一款名为《异教徒》（Heretic）的老式动作游戏。他卡在了该游戏的某个最终关卡，因此需要一些帮助来消灭怪物。

该关卡的主要部分是一条巨大的走廊（其尺度之大、宽度之窄，可将其建模为一条无限长的数轴）。走廊被划分为左右两部分；我们设分界点为 $x = 0$。

走廊的右半部分（即 $x > 0$ 区域）分布着 $n$ 只怪物——每只怪物的初始坐标 $x_i$ 已知（由于所有怪物均位于右半部分，故每个 $x_i$ 均为正数）。

走廊的左半部分（即 $x \leq 0$ 区域）布满了压碎陷阱。若某只怪物进入左半部分或到达原点（即其当前坐标 $\leq 0$），它将立即被陷阱杀死。

伊万用来消灭怪物的主要武器是“凤凰魔杖”（Phoenix Rod）。该武器可发射一枚导弹，命中后发生爆炸：爆炸会瞬间消灭所有处于爆心位置的怪物，并将其他所有怪物沿远离爆心的方向弹开。形式化地，假设伊万向坐标 $c$ 发射一枚导弹，则每只怪物将按如下规则处理：设某只怪物当前坐标为 $y$，则：

• 若 $c = y$，则该怪物被爆炸直接消灭；
• 若 $y < c$，则该怪物被向左弹开 $r$ 个单位，其新坐标变为 $y - r$；
• 若 $y > c$，则该怪物被向右弹开 $r$ 个单位，其新坐标变为 $y + r$。

伊万消灭怪物的过程如下：首先选择某个整数坐标 $d$ 并向该点发射一枚导弹；待导弹爆炸、所有被向左弹入走廊左半部分（即坐标 $\leq 0$）的怪物被陷阱杀死后，若仍有至少一只怪物存活，则再次选择一个整数坐标（可以与之前使用过的坐标相同）并发射一枚导弹；如此反复，直至所有怪物全部死亡。

问：伊万最少需要发射多少枚导弹才能消灭所有怪物？你可以假设：每次伊万使用凤凰魔杖时，都会以最优方式选择爆炸点。

你需要回答 $q$ 个相互独立的查询。

The first line contains one integer $q$ ($1 \le q \le 10^5$) — the number of queries.

The first line of each query contains two integers $n$ and $r$ ($1 \le n, r \le 10^5$) — the number of enemies and the distance that the enemies are thrown away from the epicenter of the explosion.

The second line of each query contains $n$ integers $x_i$ ($1 \le x_i \le 10^5$) — the initial positions of the monsters.

It is guaranteed that sum of all $n$ over all queries does not exceed $10^5$.

第一行包含一个整数 $q$（$1 \le q \le 10^5$）—— 查询次数。

每次查询的第一行包含两个整数 $n$ 和 $r$（$1 \le n, r \le 10^5$）—— 敌人的数量，以及敌人被爆炸中心击退的距离。

每次查询的第二行包含 $n$ 个整数 $x_i$（$1 \le x_i \le 10^5$）—— 怪物的初始位置。

保证所有查询中 $n$ 的总和不超过 $10^5$。

For each query print one integer — the minimum number of shots from the Phoenix Rod required to kill all monsters.

对于每个查询，输出一个整数——使用凤凰魔杖消灭所有怪物所需的最少射击次数。

In the first test case, Ivan acts as follows:

• choose the point $3$, the first monster dies from a crusher trap at the point $-1$, the second monster dies from the explosion, the third monster is pushed to the point $7$;
• choose the point $7$, the third monster dies from the explosion.

In the second test case, Ivan acts as follows:

• choose the point $5$, the first and fourth monsters die from the explosion, the second monster is pushed to the point $1$, the third monster is pushed to the point $2$;
• choose the point $2$, the first monster dies from a crusher trap at the point $0$, the second monster dies from the explosion.

在第一个测试用例中，Ivan 的操作如下：

• 选择位置 $3$，第一只怪物在位置 $-1$ 处被压路陷阱消灭，第二只怪物被爆炸消灭，第三只怪物被推至位置 $7$；
• 选择位置 $7$，第三只怪物被爆炸消灭。

在第二个测试用例中，Ivan 的操作如下：

• 选择位置 $5$，第一只和第四只怪物被爆炸消灭，第二只怪物被推至位置 $1$，第三只怪物被推至位置 $2$；
• 选择位置 $2$，第一只怪物在位置 $0$ 处被压路陷阱消灭，第二只怪物被爆炸消灭。