122. A rectangle is inscribed in a circle of radius $R$, and the midpoints of its sides are sequentially connected. Find the perimeter of the resulting quadrilateral.
122. Let $K, L, M, P$ be the midpoints of the sides of the inscribed rectangle $A B C D$ (Fig. 20). In the right triangle $A B C$, the segment $K L$ is the midline, i.e., $|K L|=\frac{1}{2}|A C|=R$. Similarly, we prove that $|K P|=|P M|=|M L|=R$. Therefore, the quadrilateral $K P M L$ is a rhombus, and its perimeter is $4 R$.