CF650A.Watchmen

Watchmen are in a danger and Doctor Manhattan together with his friend Daniel Dreiberg should warn them as soon as possible. There are n watchmen on a plane, the i-th watchman is located at point (x__i, y__i).

They need to arrange a plan, but there are some difficulties on their way. As you know, Doctor Manhattan considers the distance between watchmen i and j to be |x__i - x__j| + |y__i - y__j|. Daniel, as an ordinary person, calculates the distance using the formula .

The success of the operation relies on the number of pairs (i, j) (1 ≤ i < j ≤ n), such that the distance between watchman i and watchmen j calculated by Doctor Manhattan is equal to the distance between them calculated by Daniel. You were asked to compute the number of such pairs.

守望者们正处于危险之中，曼哈顿博士与其朋友丹尼尔·德雷伯格必须尽快向他们发出警报。平面上共有 $n$ 名守望者，其中第 $i$ 名守望者位于点 $(x_i,\,y_i)$。

他们需要制定一个行动计划，但在执行过程中遇到了一些困难。众所周知，曼哈顿博士计算守望者 $i$ 与守望者 $j$ 之间的距离采用的是曼哈顿距离：$|x_i - x_j| + |y_i - y_j|$；而丹尼尔作为一名普通人，则使用欧几里得距离公式计算：。

此次行动的成功取决于满足如下条件的数对 $(i,\,j)$（其中 $1 \le i < j \le n$）的个数：即曼哈顿博士所计算的守望者 $i$ 与守望者 $j$ 之间的距离，恰好等于丹尼尔所计算的二者之间的距离。你需要计算出满足该条件的数对个数。

The first line of the input contains the single integer n (1 ≤ n ≤ 200 000) — the number of watchmen.

Each of the following n lines contains two integers x__i and y__i (|x__i|, |y__i| ≤ 109).

Some positions may coincide.

输入的第一行包含一个整数 $n$（$1 \leq n \leq 200\,000$）—— 表示守卫的人数。

接下来的 $n$ 行，每行包含两个整数 $x_i$ 和 $y_i$（$|x_i|, |y_i| \leq 10^9$）。

某些位置可能重合。

Print the number of pairs of watchmen such that the distance between them calculated by Doctor Manhattan is equal to the distance calculated by Daniel.

输出满足以下条件的守夜人对数：由曼哈顿博士计算出的距离等于由丹尼尔计算出的距离。

In the first sample, the distance between watchman 1 and watchman 2 is equal to |1 - 7| + |1 - 5| = 10 for Doctor Manhattan and for Daniel. For pairs (1, 1), (1, 5) and (7, 5), (1, 5) Doctor Manhattan and Daniel will calculate the same distances.

在第一个样例中，守卫 1 与守卫 2 之间的距离，对于曼哈顿博士而言为 $|1 - 7| + |1 - 5| = 10$，而对于丹尼尔而言则为 。对于点对 $(1, 1)$、$(1, 5)$ 和 $(7, 5)$、$(1, 5)$，曼哈顿博士与丹尼尔计算出的距离相同。