In the given figure, $\mathit{A}\mathit{B}\mathit{C}\mathit{D}$ is a square of side $21\mathrm{cm}.\mathit{A}\mathit{C}$ and $\mathit{B}\mathit{D}$ are two diagonals of the square. Two semi circles are drawn with $\mathit{A}\mathit{D}$ and $\mathit{B}\mathit{C}$ as diameters. Find the area of the shaded region. (Take $\mathit{\pi }=22∕7)$ .