Two players play a game using the interval $[0,33]$ on the $x$-axis. The first player randomly chooses a square of side length $s∈Z_+$ , which has a side that lies entirely on the interval. The second player randomly chooses a circle with radius $r∈Z_+$ , which has a diameter that lies entirely on the interval. After repeating choosing random squares and circles in this fashion, the players realize that the probability that the circle and square intersect is $1/2$. Let $S=\{(s,r):$ probability of intersection is $1/2 \}$ . Determine $\sum_{(s,r)∈S} (s+r)$.