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w..1.....__.....1..w
w.a......__......b.w
w...+....__....=...w
w........__........w
w.a....1.__.1....b.w
w........__........w
w...A..2.__.2..B...w
w........__........w
w.a....3.__.3....b.w
w........__........w
w...+....__....=...w
w.a......__......b.w
w..3.....__.....3..w
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