双体 - Problem

#16466. 双体

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AI Translation — This statement was translated using AI and may contain inaccuracies. Please refer to the original statement if in doubt.

一家商店成对地出售糖果。

有 $N$ 件商品。第 $i$ 件商品包含一对糖果：一颗类型为 $A_i$，另一颗类型为 $B_i$。$A_i$ 和 $B_i$ 可能相同。

如果你购买两件不同的商品，你总共会获得四颗糖果。有一对双胞胎，你想给他们每人恰好两颗糖果。只有当两个孩子收到的糖果类型的多重集（multiset）完全相同时，双胞胎才会感到满意。

计算选择两件不同商品的方法数，使得能够以这种方式将糖果分给双胞胎。

输入格式

输入格式如下：

N
A_1 B_1
A_2 B_2
:
A_N B_N

数据范围

$2 \le N \le 300\,000$
$1 \le A_i, B_i \le N$ ($1 \le i \le N$)
所有输入值均为整数。

输出格式

在单行中输出答案。

样例

输入样例 1

输出样例 1

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