← 返回题目
题库练习 Desert
← 上一题 下一题 →

A14585 | Desert

时间限制1s
内存限制256MB
通过 / 提交0/0

题目描述

You are given an undirected graph of $N$ nodes and $M$ edges, $E_1, E_2, \dots E_M$ .

A connected graph is a cactus if each of it's edges belogs to at most one simple cycle. A graph is a desert if each of it's connected components is a cactus.

Find the number of pairs $(L, R)$ , ( $1 \leq L \leq R \leq M$ ) such that, if we delete all the edges except for $E_L, E_{L+1}, \dots E_R$ , the graph is a desert.

输入格式

The first line contains two integers $N$ and $M$ ( $2 \leq N \leq 2.5 \times 10^5$ , $1 \leq M \leq 5 \times 10^5$ ). Each of the next $M$ lines contains two integers. The $i$ -th line describes the $i$ -th edge. It contains integers $U_i$ and $V_i$ , the nodes connected by the $i$ -th edge ( $E_i=(U_i, V_i)$ ). It is guaranteed that $1 \leq U_i, V_i \leq N$ and $U_i \neq V_i$ .

输出格式

The output contains one integer number – the answer.

输入输出样例

输入 #1
5 6
1 2
2 3
3 4
4 5
5 1
2 4
输出 #1
20
输入 #2
2 3
1 2
1 2
1 2
输出 #2
5
C++ 编辑器
输入
输出