Problem Description 问题描述
We already know of the large corporation where Polycarpus works as a system administrator. The computer network there consists of n computers and m cables that connect some pairs of computers. In other words, the computer network can be represented as some nondirected graph with n nodes and m edges. Let’s index the computers with integers from 1 to n, let’s index the cables with integers from 1 to m.
Polycarpus was given an important task — check the reliability of his company’s network. For that Polycarpus decided to carry out a series of k experiments on the computer network, where the ith experiment goes as follows:
 Temporarily disconnect the cables with indexes from $l_i$ to $r_i$, inclusive (the other cables remain connected).
 Count the number of connected components in the graph that is defining the computer network at that moment.
 Reconnect the disconnected cables with indexes from $l_i$ to $r_i$ (that is, restore the initial network).
Help Polycarpus carry out all experiments and for each print the number of connected components in the graph that defines the computer network through the given experiment. Isolated vertex should be counted as single component.
Input 输入
The first line contains two spaceseparated integers $n, m (2 ≤ n ≤ 500; 1 ≤ m ≤ 10^4)$ — the number of computers and the number of cables, correspondingly.
The following m lines contain the cables’ description. The ith line contains spaceseparated pair of integers $x_i, y_i (1 ≤ x_i, y_i ≤ n; xi ≠ y_i)$ — the numbers of the computers that are connected by the ith cable. Note that a pair of computers can be connected by multiple cables.
The next line contains integer $k (1 ≤ k ≤ 2·10^4)$ — the number of experiments. Next k lines contain the experiments’ descriptions. The ith line contains spaceseparated integers $l_i, r_i (1 ≤ l_i ≤ r_i ≤ m)$ — the numbers of the cables that Polycarpus disconnects during the ith experiment.
Output 输出
Print $k$ numbers, the ith number represents the number of connected components of the graph that defines the computer network during the ith experiment.
Sample Input 样例输入
6 5
1 2
5 4
2 3
3 1
3 6
6
1 3
2 5
1 5
5 5
2 4
3 3
Sample Output 样例输出
4
5
6
3
4
2
思路
由于本题的$n$很小,所以我们可以开一个前缀并查集$pre$和一个后缀并查集$suf$,对于每次查询,我们只要对前缀的$1,l1$部分和后缀的$r+1,m$部分手动合并即可.
代码
1 
