2/π2 s2 / \pi^{2} \mathrm{~s}2/π2 s
π2/2 s\pi^{2} / 2 \mathrm{~s}π2/2 s
π/2 s\pi / 2 \mathrm{~s}π/2 s
π2/4 s\pi^{2} / 4 \mathrm{~s}π2/4 s