\[\boxed{\mathbf{997\ (997)}\mathbf{.}\mathbf{\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[AB = CD\]
\[BC = AD\]
\[OC = AO\]
\[OD = OB\]
\[\angle A = \angle C\]
\[\angle B = \angle D\]
\[\mathrm{\Delta}ABO = \mathrm{\Delta}COD\]
\[\mathrm{\Delta}ABC = \mathrm{\Delta}ACD\]