Merry lives in Johnny’s backyard. But there is one problem. Johnny’s father — a botanist — has grown a couple of rare trees there. Now he is afraid that Merry can hurt their delicate bark. So Johnny is planning to protect the trees.
He has found three long planks at his old workshop, so now is going to surround his trees by a triangular fence. No part of the plank must be outside the fence, because somebody could step upon it and fall down.
It may turn out that it is impossible to surround all the trees. In this case Johnny wants to surround as many trees as possible. His father is still planning to use planks in some other way afterwards, so Johnny mustn’t cut them to pieces.
Help Johnny to find out how many trees he can save.
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