#P6859. Easy NPC Problem

Easy NPC Problem

Problem Description

It is preferrable to read the pdf statment.

Cuber QQ fell in love with research of NPC problem. He is very passionate in those cutting-edge thinkings, especially in Hamiltonian path problem, which is a well-known typical NPC problem.

In the mathematical field of graph theory, a Hamiltonian path is a path in an undirected or directed graph that visits each vertex exactly once. Mathematicians have spent hundreds of years, trying to find a general yet elegant solution of this problem, but still, the problem is only solved in a limited scope.

Cuber QQ wants to take one step forward, by solving the Hamiltonian path problem in the grid. A grid has $n \times m$ vertices. We use a typical coordinate system in the grid, where each vertex on the grid is labelled by a pair of integers $(x, y)$ $(1 \le x \le n, 1 \le y \le m)$, and it is connected to adjacent vertices (if they are available), i.e., $(x-1, y)$, $(x+1, y)$, $(x, y-1)$, $(x, y+1)$.

The problem seems too trivial to him, Cuber QQ will take another step forward to find a Hamiltonian path in the grid without visiting the vertex $(N_x,N_y)$ $(1 \le N_x \le n, 1 \le N_y \le m)$, and the starting vertex must be located at $(S_x,S_y)$ $(1 \le S_x \le n, 1 \le S_y \le m)$. It is a little too difficult for him now and he asks you for help.

Input

The first line contains an integer $T$ ($T \le 2~500$), denoting the number of test cases.

Each test case has six space-separated integers $n,m,N_x,N_y,S_x,S_y$ ($1\le N_x,S_x\le n \le 200$, $1\le N_y, S_y\le m \le 200$, $N_x\neq S_x$ or $N_y \neq S_y$) in one line.

It is guaranteed that $\sum n+m\le 10^5$.

Output

For each test case, if there is no solution, print a single integer $-1$ in one line, otherwise the first line output an integer $nm - 1$, which is the length of the path. The next $nm - 1$ lines contain the vertices in the visiting order. and each of the $n$ lines contains two space-separated integers $x,y$ ($1 \le x \le n, 1 \le y \le m$).

If there are multiple solutions, print any.

2 2 4 1 2 1 1 2 4 2 2 1 1
7 1 1 2 1 2 2 2 3 2 4 1 4 1 3 -1