Problem Statement
You are given a connected simple undirected graph with $N$ vertices and $\displaystyle\frac{3}{2}N$ edges, where $N$ is a positive even number. The vertices are labeled from $1$ to $N$, and the $i$-th edge connects vertex $A_i$ and vertex $B_i$. Moreover, for every vertex, the number of incident edges is exactly $3$.
You will color each vertex of the given graph either black ( B ) or white ( W ). Here, the string obtained by arranging the colors ( B or W ) of the vertices in the order of vertex labels is called a color sequence.
Determine whether there is a color sequence that cannot result from performing the following operation once when all vertices are colored, and if there is such a color sequence, find one.
Operation: For each vertex $k = 1, 2, \dots, N$, let $C_k$ be the color that occupies the majority (more than half) of the colors of the vertices connected to $k$ by an edge. For every vertex $k$, change its color to $C_k$ simultaneously.
There are $T$ test cases to solve.
Constraints
$T \geq 1$$N \geq 4$- The sum of
$N$over the test cases in each input file is at most$5 \times 10^4$. $N$is an even number.$1 \leq A_i < B_i \leq N \ \ \left(1 \leq i \leq \displaystyle\frac{3}{2}N\right)$$(A_i, B_i) \neq (A_j, B_j) \ \ \left(1 \leq i < j \leq \displaystyle\frac{3}{2}N\right)$- The given graph is connected.
- Each vertex
$k \ (1 \leq k \leq N)$appears exactly$3$times as$A_i, B_i \ \left(1 \leq i \leq \displaystyle\frac{3}{2}N\right)$.
Input
The input is given from Standard Input in the following format:
T
\mathrm{case}_1
\mathrm{case}_2
\vdots
\mathrm{case}_T
Each test case $\mathrm{case}_i \ (1 \leq i \leq T)$ is in the following format:
N
A_1 B_1
A_2 B_2
\vdots
A_{\frac{3}{2}N} B_{\frac{3}{2}N}
Output
Print $T$ lines. For the $i$-th line, if there is a color sequence that cannot result from performing the operation for the $i$-th test case, print such a color sequence; otherwise, print -1. If there are multiple color sequences that cannot result from performing the operation, any of them will be considered correct.
样例
2
4
1 2
1 3
1 4
2 3
2 4
3 4
10
1 2
1 3
1 4
2 3
2 4
3 5
4 5
5 6
6 7
6 8
7 9
7 10
8 9
8 10
9 10
BWWW
BWWWBWWWBB
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