A bug travels in the coordinate plane moving only along the lines that are parallel to the x-axis or y-axis. Let and . Consider all possible paths of the bug from to of length at most 14. How many points with integer coordinates lie on at least one of these paths?
Hint 1: Note that the Manhattan distance between and is 10. A point lies on a path of length at most 14 if and only if .
Hint 2: Write the Manhattan distance sum as an inequality: .
Hint 3: Analyze this inequality for different quadrants/regions of to count all valid integer coordinates.
Let the bug move on the integer lattice. The Manhattan distance between and is:
We are considering all paths of length at most .
A point lies on at least one path from to of length at most 14 if and only if:
where is the Manhattan distance.
This defines a bounding region in the coordinate plane. By dividing the plane into sectors based on the absolute value boundaries, we count the number of integer lattice points satisfying this inequality. The count of such lattice points is exactly .
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