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The bank has been broken into, and all the local mafia thugs have an unusual alibi: they were at home playing Connect 4! In order to assist with the investigation, you are asked to write a program to validate all the Connect 4 boards that have been seized in order to check that the positions are indeed positions from a valid Connect 4 game, and have not been hastily put together as soon as the police knocked on the door. The rules for connect 4: players R and Y take it in turns to drop tiles of their colour into columns of a 7x6 grid. When a player drops a tile into the column, it falls down to occupy the lowest unfilled position in that column. If a player manages to get a horizontal, vertical or diagonal run of four tiles of their colour on the board, then they win and the game ends imme...