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 Abstract We present the complete solution of the following problem of 
G. Pólya: Circular forest has a center at the origin and radius $R\geq 1$. A 
person is staying at the center and the trees of the radius $r$ are planted at 
all other lattice points of the forest. Determine the maximal value $\rho$ of 
the radius $r$ for which the person can see out of the forest and, in the case 
$r=\rho$, determine the directions in which he/she should look in order to see 
out of the forest. 
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