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|1 초||128 MB||27||13||4||33.333%|
The knight is getting bored of seeing the same black and white squares again and again and has decided to make a journey around the world. Whenever a knight moves, it is two squares in one direction and one square perpendicular to this.
The world of a knight is the chessboard he is living on. Our knight lives on a chessboard that has a smaller area than a regular 8 × 8 board, but it is still rectangular. Can you help this adventurous knight to make travel plans?
The eight possible moves of a knight
Find a path such that the knight visits every square once. The knight can start and end on any square of the board.
The input begins with a positive integer n in the first line. The following lines contain n test cases.
Each test case consists of a single line with two positive integers p and q, such that 1 ≤ p · q ≤ 26. This represents a p × q chessboard, where p describes how many different square numbers 1, . . . , p exist, q describes how many different square letters exist. These are the first q letters of the Latin alphabet: A, . . .
The output for every scenario begins with a line containing "Scenario #i:", where i is the number of the scenario starting at 1. Then print a single line containing the lexicographically first path that visits all squares of the chessboard with knight moves followed by an empty line. The path should be given on a single line by concatenating the names of the visited squares. Each square name consists of a capital letter followed by a number.
If no such path exist, you should output impossible on a single line.
3 1 1 2 3 4 3
Scenario #1: A1 Scenario #2: impossible Scenario #3: A1B3C1A2B4C2A3B1C3A4B2C4