(10 points) As shown in the figure, a tree is planted every 3 meters starting from point 0. If 3 "Protect Trees" signs are hung on 3 trees, then no matter how they are hung, the distance between at least two of the signed trees is even (in meters). Try to explain the reason.
Problem 956
Official solution
【Answer】Solution: The distance between the two farthest apart wooden signs is equal to the sum of their respective distances from the middle sign. If the distances between the three signs are all odd, it would result in "odd + odd = odd", which is clearly not true. Therefore, there must be two signs whose distance is even.
Answer: No matter how they are hung, there will be at least two sign-hanging trees whose distance is even.