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2023 SSMO Relay Round 3 Problems/Problem 3

Problem

Let $T=$ TNYWR. Let $n = N+1.$ A spray painter has a paint gun that paints all areas within a radius of $2.$ The spray painter walks in the following locations, where red lines indicate red paint coming out of the gun and blue lines indicate blue paint coming out of the gun. The spray painter starts from the outermost square and works his way inwards, where in the end. The positive difference between the area of the blue-painted region and the area of the red-painted region is $a+b\pi.$ Find $a+b.$ (Note: if a spray painter paints an area with multiple colors, only the last color will be showing).

[asy] unitsize(7mm); label("(1,1)",(1,1.5)); label("(-1,1)",(-1,1.5)); label("(-1,-1)",(-1,-1.5)); label("(1,-1)",(1,-1.5)); label("(2,2)",(2,2.5)); label("(-2,2)",(-2,2.5)); label("(-2,-2)",(-2,-2.5)); label("(2,-2)",(2,-2.5)); label("(3,3)",(3,3.5)); label("(-3,3)",(-3,3.5)); label("(-3,-3)",(-3,-3.5)); label("(3,-3)",(3,-3.5)); label("(N,N)",(9,9.5)); label("(-N,-N)",(-9,-9.5)); label("(-N,N)",(-9,9.5)); label("(N,-N)",(9,-9.5)); label("(N-1,N-1)",(7.3,8.5)); label("(-N+1,-N+1)",(-7.3,-8.5)); label("(-N+1,N-1)",(-7.3,8.5)); label("(N-1,-N+1)",(7.3,-8.5)); label("(N-2,N-2)",(5.5,7.5)); label("(-N+2,N+2)",(-5.5,-7.5)); label("(-N+2,N-2)",(-5.5,7.5)); label("(N-2,-N+2)",(5.5,-7.5)); draw((1,1)--(-1,1)--(-1,-1)--(1,-1)--cycle,red); draw((2,2)--(-2,2)--(-2,-2)--(2,-2)--cycle,blue); draw((3,3)--(-3,3)--(-3,-3)--(3,-3)--cycle,red); draw((7,7)--(-7,7)--(-7,-7)--(7,-7)--cycle,red); draw((8,8)--(-8,8)--(-8,-8)--(8,-8)--cycle,blue); draw((9,9)--(-9,9)--(-9,-9)--(9,-9)--cycle,red); dot((1,1),red); dot((-1,1),red); dot((1,-1),red); dot((-1,-1),red); dot((2,2),blue); dot((-2,2),blue); dot((2,-2),blue); dot((-2,-2),blue); dot((3,3),red); dot((-3,3),red); dot((3,-3),red); dot((-3,-3),red); dot((7,7),red); dot((-7,7),red); dot((7,-7),red); dot((-7,-7),red); dot((8,8),blue); dot((-8,8),blue); dot((8,-8),blue); dot((-8,-8),blue); dot((9,9),red); dot((-9,9),red); dot((9,-9),red); dot((-9,-9),red); dot((0,4)); dot((0,-4)); dot((4,0)); dot((-4,0)); dot((0,5)); dot((0,-5)); dot((5,0)); dot((-5,0)); dot((0,6)); dot((0,-6)); dot((6,0)); dot((-6,0)); [/asy]

Solution

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