CF840B.Leha and another game about graph

Leha plays a computer game, where is on each level is given a connected graph with n vertices and m edges. Graph can contain multiple edges, but can not contain self loops. Each vertex has an integer d__i, which can be equal to 0, 1 or  - 1. To pass the level, he needs to find a «good» subset of edges of the graph or say, that it doesn't exist. Subset is called «good», if by by leaving only edges from this subset in the original graph, we obtain the following: for every vertex i, d__i =  - 1 or it's degree modulo 2 is equal to d__i. Leha wants to pass the game as soon as possible and ask you to help him. In case of multiple correct answers, print any of them.

列哈正在玩一款电脑游戏，其中每一关都给出一个包含 $n$ 个顶点和 $m$ 条边的连通图。该图可以包含重边，但不能包含自环。每个顶点 $i$ 上有一个整数 $d_i$，其值只能是 $0$、$1$ 或 $-1$。为了通过这一关，他需要找出图的一个“好”边子集，或者判定这样的子集不存在。“好”子集的定义是：若仅保留该子集中的边（其余边全部删除），则对每个顶点 $i$，要么 $d_i = -1$，要么该顶点在新图中的度数模 $2$ 等于 $d_i$。列哈希望尽快通关，因此请你帮助他解决这个问题。若存在多个正确答案，输出任意一个即可。

The first line contains two integers n, m (1 ≤ n ≤ 3·105, n - 1 ≤ m ≤ 3·105) — number of vertices and edges.

The second line contains n integers _d_1, _d_2, ..., d__n ( - 1 ≤ d__i ≤ 1) — numbers on the vertices.

Each of the next m lines contains two integers u and v (1 ≤ u, v ≤ n) — edges. It's guaranteed, that graph in the input is connected.

第一行包含两个整数 $n$、$m$（$1 \leq n \leq 3 \cdot 10^5$，$n - 1 \leq m \leq 3 \cdot 10^5$）——顶点数和边数。

第二行包含 $n$ 个整数 $d_1,\, d_2,\, \dots,\, d_n$（$-1 \leq d_i \leq 1$）——各顶点上的数字。

接下来的 $m$ 行中，每行包含两个整数 $u$ 和 $v$（$1 \leq u,\, v \leq n$）——边。保证输入中的图是连通的。

Print  - 1 in a single line, if solution doesn't exist. Otherwise in the first line k — number of edges in a subset. In the next k lines indexes of edges. Edges are numerated in order as they are given in the input, starting from 1.

如果不存在解，在单独一行输出 -1。否则，第一行输出子集中的边数 $k$；接下来的 $k$ 行每行输出一条边的编号。边的编号按输入顺序从 1 开始计数。

In the first sample we have single vertex without edges. It's degree is 0 and we can not get 1.

在第一个样例中，我们有一个没有边的孤立顶点。它的度数为 0，因此无法得到 1。