Let $ ABCD$ be a convex quadrilateral with $ AB=AD$ and $ BC=CD$. On the sides $ AB,BC,CD,DA$ we consider points $ K,L,L_1,K_1$ such that quadrilateral $ KLL_1K_1$ is rectangle. Then consider rectangles $ MNPQ$ inscribed in the triangle $ BLK$, where $ M\in KB,N\in BL,P,Q\in LK$ and $ M_1N_1P_1Q_1$ inscribed in triangle $ DK_1L_1$ where $ P_1$ and $ Q_1$ are situated on the $ L_1K_1$, $ M$ on the $ DK_1$ and $ N_1$ on the $ DL_1$. Let $ S,S_1,S_2,S_3$ be the areas of the $ ABCD,KLL_1K_1,MNPQ,M_1N_1P_1Q_1$ respectively. Find the maximum possible value of the expression: $ \frac{S_1+S_2+S_3}{S}$