Write a program that uses recursive backtracking to play the game of Boggle. Boggle is a word game played on a 4 x 4 grid where the player tries to find all valid dictionary words that can be made by tracing a path between adjacent letters from the board. Each link in the path can be horizontal, vertical, or diagonal. Figure 12.18 shows an example path to form the word “ensure”. Use recursive backtracking to explore each possible word that can be made using the letters on the board. Your algorithm should choose a starting square, explore what can be made from there, and un-choose the square afterward.

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