Solution
56. b8=♛+ ♚xb8 57. ♜b3 ♚c7 58. ♜xb5
The position
This advanced puzzle (rating 1933) asks White to move to find the winning idea. It features these themes: Promotion, Pin.
It is White to move. Look for the tactic hiding in the position — Promotion, Pin. Drag a piece on the board to play your move; the puzzle will tell you if you found the best continuation.
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